Very good thought process. I would disagree, and lean towards the U.S. using the majority of its power against the European Axis. In my opinion, Sealion is a move which can actually weaken the Germans more than it may strengthen them, especially because of how much more powerful it makes Russia-not to mention the losses Germany can take from the amphibious/air assault.
This makes thing better for America to go into Europe, because a key part of Axis and Allies-I think, at least-is putting more pressure on the weakest parts of the enemy rather than going into more of a “fair fight” against their stronger points. After Sealion, America and Russia have the opportunity to conduct a very dangerous-for the Germans-offensive from West and East, respectively. Japan’s progress should not be enough to counter this, I think. Just like in Original, 1941, 1942, and Global, the ability of the Allies to crush Germany in a multi-front war seems to be key, even if Japan gets dangerously close to the verge of winning in the meantime. See Donray’s essays online(he wrote some brilliant strategy for Original that is still applicable in some ways to Global 1940.)
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