Interesting idea. Sort of an “all or nothing” move for the Axis. If they manage to take Washington, basically taking USA out of the game, then they will all probably have enough money and strength to go back to Europe and the Pacific to mop up the other Allies. Once Japan deals with the large US Navy, it could more or less have a field day throughout the rest of the Pacific and on Asia. If Germany had enough troops to hold off Russia, they could probably do Sealion now and get ready for Barbarossa. If the Brits didn’t do too much damage to the Med and/or Italy’s home territories, they ought to have not much trouble going back and cleaning out the Med and Africa, espeically if Germany does do Sealion successfully.
However, if they lose in Washington, I think all three Axis will have left themselves too weak after commiting so much resources to this plan. Like you said, Japan will start getting pummelled by ANZAC, India and China. Plus, they will still have that large US fleet to deal with which can now still grow and replace losses. Britian will be giving the Italians fits in Africa and probably trying hard to get Gibraltar back. Not sure how strong Russia will be or how much they will be able to bother the Germans offensively. I guess that depends on how much Germany was able to put up along the border in addition to all the hardware sent to America.
I think this plan could work for you one time. The next game you played, if you started moving your ships in the same manner, the US player would be like “Not Again!” and buy much differently, thus foiling your plans. I guess they couldn’t attack any Axis navy until after round 3, so I would bet they would simply stock up on ground units. Even so, with the US only haveing Minor ICs until at war, they wouldn’t be able to build too much there. If Italy or Germany could take the Panama Canal first, allowing Japanese Transports to go through and attack Eastern US along with a bunch of planes from both sets of carriers, this might still be possible even if the US player figures out what you are up to. You know, with the US being neutral for 3 rounds and Axis ships being able to float peacefully through their waters during that time, it can really be a detriment to the US survival in this game. Plus since Russia is neutral until round 4, the only other Ally you have to worry about is Britain, who is fairly weak early in the game once the Luftwaffe trashes the Royal Navy G1. You might have found a gaping flaw here.