I do regard the battle of the Atlantic as one of those underrated turning points, but the questions are
a) how long can the Germans keep it up before the Americans get involved?
b) how many more subs and FW-200s can the Germans make?
c) as I recall, Coastal Command was on a shoestring compared to say, Bomber Command. Even taking into account increased sub and Condor production, can they beat a beefed up RAF CC and a Royal Navy getting even more resources poured into it?
Good questions.
The first relies on the wider political aspects of the war - if the Americans aren't going to get involved (ie the isolationist wing wins out), then they'll stop trying to send/support convoys before they tool up and start sending their young men off to die in another continent's war (is the line that the isolationists would prefer). Opens a wider question of what it would take to make them join in (and the Pearl Harbour debate comes in)
The second - all depends on what their priorities will be. With 20-20 hindsight, we can see what they probably should have focused resources on, or not. Again, no straightforward answer.
The third - no. The entire problem was that Coastal Command (aka 'Cinderella Command') was the red-haired stepchild of the RAF. Coupled with the obsession towards offensive activity and near-contempt of defensive operations ("Wars are not won by
defence, you know!"), it gave the Germans an opportunity that should have been closed down far sooner. Bomber Command kept haranguing all levels of authority for more resources at the expense of Coastal Command and others ("We're the only ones who can strike back!"), the dogma of the one true air offensive (fetishised since Trenchard) precluded the effective defence of convoys for far too long. Even when Bomber Command had the resources allocated to it, they refused to help by bombing the U-boat pens being constructed in France after the fall of France, before the lengthy bomb-proofing work was completed there. Because it would "distract from the essential offensive".
We knew from 1918 that convoys, protected from the air, were the way ahead, but this was originally deemed "too defensive"*. We even had, written down, the correct description of ideal air escort behaviour. And we
knew that it was actually not merely defensive**
Even when, begrudgingly, convoys were adopted, and escorts provided from the air, the actual provision of non-obsolete aircraft and weapons that would work was like pulling teeth. And then, when the U-boat pens in France were completed, the bright idea of "You know, let's try to attack the U-boats in the Bay of Biscay before they get to the wider Atlantic" became paramount. Which was fine on the face of it, but as the U-boats didn't have to attack, they could, you know, head out under water. Which was far harder to detect. And the Bay of Biscay turns out to be pretty bloody big.
With decent aerial cover, the only chance U-boats really had was at night. The Leigh Light was successfully trialled in May 1941, but overlooked by the RAF. ASV II (centimetric radar for the aircraft) was available already then as well. Long range aircraft, plus Leigh Lights and ASV-II, coupled with firm adherence to the convoy system would have effectively ended the Battle of the Atlantic by summer 1941. The lure of the Bay of Biscay and the attempts to interdict the passage of the U-boats in this comparatively restricted space was fully understandable and definitely worth the attempt, but should have been clearly subordinate to the overriding purpose of providing full air cover to all convoys.
Of course, the Germans themselves made numerous errors - the near-total lack of co-ordination between the Luftwaffe and the U-boats really didn't help them at all.
Ahem. Sorry - I can go on for ages on this. (I have a 4000 word essay on this subject at hand - it was my essay subject at Intermediate Command and Staff College. And yes, airships were in it).
*‘I always sought to rupture this defensive obsession by searching for forms of counter-offensive … I could not rest content with the policy of “convoy and blockade' - Winston Churchill
**'...the convoy system, with adequate surface and air escort, far from being defensive was highly offensive in character, for not only did it prevent ships from being sunk but the escorts destroyed more U-boats than any other method of direct attack’ - Air Historical Branch Narrative on the U-boat battle, 1918.