Have the UK begin to purchase fleet on UK1 once he sees Jap trannies are staying north. Focus on getting the UK income as high as humanly possible. Also, have the UK starting land units begin to push hard into china, along with the starting china units to kick japan out of asia ASAP. Do not fear declaring war on Japan if they are going after the US anyway, it doesn’t matter.
Have ANZAC focus on subs and planes. Subs for raiding, planes for defending. Try to make a stand with the US fleet at Pearl, this will keep japan’s fleet from moving back into position after the US grab for a few extra turns.
Get a chuckle when japan realizes western us is only worth 10, not 50.
That is really all one can do sadly. Also you can block with 1 DD, then 1 Cru to SZ 7. Without passing threw SZ 7 japan has no way to reach alaska delaying them 1 more turn. Or at least giving you 1 turn with war economy with any luck.
Edit: Just to add I think the best method the US has to stop this is blocking SZ 7, this forces you to land on the islands and use British Colombia as your LZ for your planes on a J4 strike. At the end of J3 you would have 20 land units in BCO at the most. This means the US, on turn 3, would need to be able to kill said 20 land units. By US3 at max a US player should have 3 inf, 1 mech, 1 art, 1 arm (starting) 2 inf (pearl) 3 fig, 3 tac, 3 bmr, plus 3 inf/2 art (T1 buy), plus 6 inf/1 art (T2 buy). Or 14 inf, 1 mech, 4 art, 1 arm, 3 fig, 3 tac, 3 bmr. Or 29 hits /w 63 punch. This tactic would allow the US to hold for atleast 1 more turn.
Now an easy J counter would be to move starting transports into SZ 2 on J1 /w navy. This is an interesting puzzle, but there must be a way to stop it. And even if it cannot be stopped, I think UK could take the win anyway.