Move all?
I think that is a bit too risky,
Always keep the backdoor secured, do not trust the quietness, they will be there way before you can come back.
If the US saves some money, buys hell of a navy and you are in Africa?
It would take you around 3 turns to sail all the way back, assuming you are at Cape of Good Hope, or you can buy new stuff, say you have 36 IPC, that’s a battleship and a destroyer,
I think it is very, just say, stupid to leave nothing behind, although they might build transports a turn later and invade even later on, you’ve got a big navy fight, losing all your money on ships, not beating Russia anymore, risking the position of Germany, and being disabled of any combat except the naval war in the pacific for like 3-5 rounds? (just a wild guess)
I would not leave Tokyo behind with nothing, never.