Most likely with Italy neutral, Greece and Yugoslavia remain neutral albeit Axis-leaning. It was the Italian quagmire that forced the Germans to deal with Greece and that in turn provoked the Yugoslav affair; Hitler's intentions was to tolerate them being neutral on the condition of signing the pact and continuing economic deals, as his concern was leaving his flank exposed with Greece being a blistering sore. None of that exists here, so it's likely Barbarossa can kick off in May of 1941. Worse, for the Soviets, there is no need to cancel the planned twin envelopment of Soviet armies being planned up until March of 1941, when the Balkans Crisis forced the diversion of 12th Army and thus cancelled that planned operation. Finally, in April of 1941 IOTL Stalin ordered a partial mobilization on the basis of intelligence concerning the coming Nazi attack, which ultimately led to 800,000 being called up and deployed to units in June.....just in time for the invasion. Here, the Germans are attacking as the Russians are midway through said mobilization.
All in all, it's a recipe for a knockout blow on the Soviets in 1941. That completely changes the calculus many are noting here, as there is no Anti-Axis Arab Nationalism, Communism, etc to be concerned about, nor any real patron of guns. Even if the United States attempts to step up to the plate, it's worth noting insurgencies in the 20th Century did not have a generally high success rate. There is a reason nations spend trillions collectively on defense instead of relying on militias in the modern day.