I just thought of another possibility. Suppose the Axis do this and attack Washington. Then, say the US has just enough defense to hold out, or the Japs get bad dice, whatever but the result is the invasion fails, the US keep Washington and stay in the game. What if some US troops, or even possibly ANZAC troops, managed to re-take the Panama Canal? Then, here is Japan with all of their navy trapped in the Atlantic with no land troops or air force left. What a DISASTER!
Assuming neither Germany or Italy was in the position to reopen the Panama Canal, by the time Japan got it’s fleet all the way around South America and back into the Pacific, I bet most of their possessions in the Pacific and Asia would be gone. Plus if they built any more navy, it would be small because they wouldn’t be making that much money yet and that large US Navy could float around and smash anything that Japan managed to build. If I were the US in that situation, once I knew my capital and homeland territories were secure, I would rush over some bombers to someplace close enough to Japan – perhaps Iwo Jima if the US could take that or even Korea if the US or USSR could take that – then SBR Japan to keep them from building too many defense units. Meanwhile, US builds some transports, men and tanks, floats them over a couple of rounds and WHAM! Japan is in the bag. By the time the Jap fleet gets around South America, their capital is gone and US can dust off the remains of the Jap fleet at it’s leisure. Or not, since that fleet doesn’t include any transports it’s not really a threat anymore, more of a nuisance.