Probably not, no, because there was no real interest in such in their respective centers of power.
This only holds true if ASBs grant the British and Soviets the ability to survive without food and to make weapons appear out of thin air.
In the absence of Lend Lease, the Germans absolutely have the ability to force the UK into favorable terms-even with American support this nearly occurred OTL-and, likewise IOTL, had the ability to defeat the USSR but here their capability to do such cannot be questioned. I cite from Denis Havlat (2017)
Western Aid for the Soviet Union During World War II: Part I,
The Journal of Slavic Military Studies:
With the Battle of Britain raging in the summer and autumn of 1940, British demand for aircraft reached new heights as well. By 1 December 1940, Britain had ordered a staggering 23,000 aircraft from the American industry, of which only 2,100 had been delivered to the beleaguered island.28 Domestic production of aircraft for that year had been 15,049 aircraft.29 While these shipments were invaluable for Britain’s survival, they came at great financial cost. In order to purchase the 50 destroyers offered by the United States, the British had to sell their possessions in the West Indies and Newfoundland, leasing them to the Americans for 99 years.30 Even then, the strains of war were too great a burden for the British economy:
British industry was incapable of producing the range and quantity of armaments required to win the war. Even those items that could be manufactured domestically were heavily dependent on imports of raw materials and products such as steel. Most of these imports came from the United States and had to be paid for either in gold or dollars… . The day of reckoning was rapidly approaching. From a total of £775 million at the beginning of 1940, Britain’s gold and dollar reserves … had fallen [by August 1940] by over a third to £490 million… . They would last another three to four months at most. By the end of 1940, therefore, Britain would be unable to carry on the war by its own efforts.31
By September 1940, British orders in the United States amounted to 10 billion dollars, of which only a fraction could be paid for.32 The country was nearing financial collapse: ‘ … by the beginning of 1941 it had less than £3 million left in its gold and dollar reserves. This was as near to bankruptcy as it was possible to go without actual default’. 33 Realizing that without American aid Britain would have to surrender or negotiate with Germany, Roosevelt devised the so-called Lend-Lease law, which took effect on 11 March 1941. This law gave the President the authority to supply any country that was considered vital for the defense of the United States.34 For the duration of the war, Britain would receive supplies free of charge, which would be handed back or repaid once the war had ended.
Further on:
Even with the deliveries received from the United States, Britain’s military position in 1941 was close to hopeless. During the first half of this year the Luftwaffe continued its bombing raids against the island, Rommel’s forces were steadily advancing in North Africa, British forces sustained yet again humiliating defeats in Greece and Crete, and the German U-boats were sinking ever more British ships. Luckily, the Americans were now supplying Britain for free. In 1941 the United States delivered 4,473 aircraft either directly to Britain, to British overseas commands, or to British colonies and dominions.35 British production of aircraft in 1941 had been 20,094 units; whereas the colonies and dominions produced around 15 percent of this number.36 Other substantial military deliveries were tanks and trucks. Around 13,000 trucks and 1,390 tanks were shipped to Britain and its overseas forces before the end of 1941.37 Domestic production in 1941 had manufactured 4,841 tanks and 88,161 military trucks.38 Food represented the most crucial non-military supply. Before the war Britain had to import twice as many tons of food from overseas sources as raised on her own land.39 However, by the summer of 1940 Britain could no longer import food from continental Europe and had to cut down its food imports from other parts of the world in order to free shipping capacity for military supplies and resources. In combination with the many shiploads of food lost to the German U-boats, this created a situation where the British nation was close to starvation. Between the fall of France and the passing of the Lend-Lease act, the average British adult lost around 4.5 kilogram of weight due to the rapidly shrinking diet.40 Between 16 April and 25 December 1941, the Americans supplied Britain with over one million tons of food, including millions of concentrated vitamin tablets to counter a vitamin shortage caused by strict rationing.41 Shipments continued to increase, delivering 1.427 million tons in 1942, 1.705 million tons in 1943, 1.28 million in 1944, and 709,000 tons in 1945.42 On average, this amount of food was sufficient to feed over 4 million people during the years 1941–1945, around 10 percent of the British population.43
Besides the deliveries sustaining the British population and industry, American aid contributed decisively in stopping Rommel’s advance in North Africa. By 24 October 1942, American deliveries to North Africa and the Middle East amounted to 900 medium tanks, including 300 Sherman tanks that were of better quality than anything the British had before, as well as ninety 105 mm self-propelled anti-tank guns, 800 light tanks, 25,000 trucks and jeeps, over 700 twin-engine medium bombers, and nearly 1,100 fighters.44 The percentage of military equipment supplied to the British armed forces from American sources was 11.5 percent in 1941, 16.9 percent in 1942, 26.9 percent in 1943, and 28.7 percent in 1944.45 Even these figures understate the full magnitude of American aid to the British Empire. In 1942 the United States supplied 9,253 tanks and 5,898 aircraft, while British industry had turned out just 8,611 tanks and 23,672 aircraft.46 In 1943 American supplies had increased to 15,933 tanks and 6,710 aircraft, while British manufacture of tanks had decreased to 7,476 and aircraft production increased only modestly to 26,263 machines.47 In 1944, at the height of these deliveries, the United States supplied the British Empire with a staggering 11,414 aircraft, while the British produced 26,461 during that year.48 Total US deliveries of aircraft to the British Commonwealth amounted to nearly 34,000 units.49 Throughout the years 1941–1944 the United States delivered between one-fifth and one-third of total British Empire aircraft production. The share of American tanks was even greater; it increased from approximately 20 percent in 1941, to 100 percent in 1942, and to 200 percent of the total British Empire production in 1943. During the last two years of the war, Britain alone received, among other things, 76,737 Jeeps, 98,207 trucks, 12,431 tanks, and 6,715 000 tons of steel and iron.50 By 1944 around two-thirds of the tanks and trucks in the British army came from the United States.51 The total value of the aid delivered to the British Empire amounted to slightly more than 30 billion dollars.52
By the summer of 1941, the island nation was fully dependent on American deliveries, having been transformed into a giant unsinkable aircraft carrier similar to the ‘Airstrip One’ described in George Orwell’s novel 1984. Without American deliveries, Britain would either have been starved into submission or collapsed financially. Even if these two scenarios could somehow have been avoided, British industry would have produced fewer weapons than historically, since it was dependent on overseas deliveries of resources from the United States. The absence of these resources, combined with the lack of Lend-Lease tanks, aircraft, motor vehicles, small arms, and artillery, would have meant a far weaker and far worse-equipped British army, navy, and air force. British victory in North Africa would have thus become unlikely, a successful Bomber Offensive improbable, and an invasion of continental Europe impossible.
Without American aid, the UK would've thus been compelled to seek a peace deal with the Germans no later than early 1941. How about the Soviets?
Western Aid for the Soviet Union During World War II: Part II by Denis Havlat:
During World War II the Soviet Union received large amounts of aid from the Western world in the form of supplies and military intervention, both of which were declared to have been irrelevant for the Soviet Union’s victory over Nazi Germany by Soviet historians. This article examines the claim made by Soviet historiography, and it comes to the conclusion that both Western supplies and military intervention were far more helpful than claimed by the Soviets. Without this aid the Red Army would not have been able to perform as well as it did historically, tilting the balance in Germany’s favor. Soviet claims about the irrelevance of Western aid can thus be dismissed as propaganda and inaccurate.
Havlat also goes further, noting how the lack of the U.S. would have further effects:
Overall, the Western Allies were responsible only for a small fraction of the losses sustained by German infantry and armor between 1941 and 1943 (around 10 percent); however, their contribution in the destruction and occupation of the Luftwaffe was overwhelming. The same applies to their contribution in forcing the Germans to leave most heavy artillery in the Reich as anti-aircraft weapons, preventing them from being used as anti-tank weapons in the East. Without Allied military intervention, the Germans could have sent at least 2,000 additional tanks, some 5,000 additional 88 mm anti-aircraft guns, around 15,000 additional aircraft, tens of thousands of additional motor vehicles, and up to half a million additional soldiers to the Eastern Front in the years 1941–1943, which would have shifted the balance in their favor.
Further on:
Without the need to fight in the Atlantic; to transport large amounts of troops, equipment, and supplies across the entire continent; and the necessity to defend against Allied bombing, Germany could have massively reduced its U-boat, locomotive, and anti-aircraft gun and ammunition production and converted at least part of these capacities into the production of more aircraft and equipment for land warfare. Additionally, without bombing, and the need to maintain a large enough army to fight on several fronts, there would have been less need to use forced labor in the factories, thus boosting production. Historically, Germany already outproduced the USSR in certain areas like locomotives, trucks, and even bombers, with 12,664 produced by Germany in the years 1941–1943 as compared to 11,359 built by the USSR.170 Without Allied intervention and Lend-Lease, Soviet margins in these areas would most likely have widened, while margins in areas such as tanks would have shrunk significantly. If Germany and its industry could have concentrated on one single front from 1941 onwards, it most likely would have vastly changed the outcome of the war in the East.
The USSR and Total War: Why Didn’t the Soviet Economy Collapse in 1942? by Mark Harrison:
Roosevelt also contributed to Soviet stabilization. The first installment of wartime Allied aid that reached the Soviet Union in 1942, although small by later standards, amounted to some 5 per cent of Soviet GNP in that year. Although Allied aid was used directly to supply the armed forces with both durable goods and consumables, indirectly it probably released resources to households. By improving the balance of overall resources it brought about a ceteris paribus increase in the payoff to patriotic citizens. In other words, Lend-Lease was stabilizing. We cannot measure the distance of the Soviet economy from the point of collapse in 1942, but it seems beyond doubt that collapse was near. Without Lend-Lease it would have been nearer. Stalin himself recognized this, although he expressed himself more directly. He told Khrushchev several times that the Soviet Union had suffered such heavy losses that without Allied aid it would have lost the war.19
Boris V. Sokolov (2007).
The role of lend‐lease in Soviet military efforts, 1941–1945, The Journal of Slavic Military Studies: Vol. 7, issue 3, pages 567-586:
In general, we can conclude that without Western supplies, the Soviet Union not only could not have won the Great Patriotic War, but was not even able to resist the German invasion, not being able to produce a sufficient amount of weapons and military equipment and provide it with fuel and ammunition. This dependence was well understood by the Soviet leadership at the beginning of the war. For example, the special envoy of President F.D. Roosevelt, G. Hopkins, reported in a message dated July 31, 1941, that Stalin believed it was impossible without American assistance from Great Britain and the USSR to resist the material might of Germany, which had the resources of occupied Europe. {70}Roosevelt, back in October 1940, announcing his decision to allow the military department to provide weapons and equipment that are surplus for the needs of the American armed forces, as well as strategic materials and industrial equipment to those countries that could protect American national interests, allowed the inclusion of these countries and Russia. {71} Without such an attitude on the part of the president, the pre-war placement in the United States of Soviet orders for equipment important for the production of weapons and military equipment would hardly have been possible.
Now, you've suggested the British atomic bomb project as a solution to the above issues; how exactly is the UK able to afford and sustain such a project with widespread starvation, being broke and without the ability to sustain its conventional forces? Indeed, even with American aid Tube Alloys was turned over to the Americans because of the British industry not being up to the task, at least not on a reasonable timescale and this was born out by the British not developing their first nuclear weapon until the 1950s. Nazi Germany fought on until physically overran, how exactly is its willpower going to break but the British-an actual Democracy with leaders beholden to the people-won't despite being in a much worse situation? It simple has no basis in reality and we already know IOTL 1940 the British were willing to accept terms and get out of the conflict.
As for the U.S. somehow getting into the conflict after 1944, again, we know that's not going to happen because even staunch German-hawks like FDR ruled such out in the eventuality the Germans defeated the USSR. See Mark Stoler's
Allies and Adversaries: The Joint Chiefs of Staff, the Grand Alliance, and U.S. Strategy in World War II, because in it the author reveals the planning of the JCS as it concerns the war and situational contingencies therein.
From Page 72:
Page 80:
Page 93:
Concurrent to these concerns, the following documents were prepared:
"Conditions under Which an Armistice Might Be Negotiated between the United Nations and the European Powers", on June 11, 1942 by Maj. Gen. George V. Strong (S Document 22)
Col. Nevins, ‘‘Courses of Action Open to the United States in the Event the Prospective 1942 German Offensive Forces Russia to Capitulate,’’ memo, Apr. 1942, and unsigned memo to Nevins, Apr. 25, 1942, Wedemeyer Papers, box 76, folder 2, HI