First things first, watch the economics, as long as you are making MORE money, you are in charge, and can trade piece for piece all day.
Second thing, remember you only need to NOT LOSE Hawaii and NSW. Get stacks of ground units into those territories - mixed with planes + an AA and hold.
Third, as often as possible build Transports and Men. Take islands, forcing Japan to take them back, even if it costs you the tran to steal the territory in the first place. Again, try to watch the economics here.
What this all does - is dilute’s Japan’s ability to focus it’s economics on one specific target. If Japan can’t focus and take it’s objectives, it can’t win. If you slowly start to swing the economic balance in your favour - 1 island at a time, eventually Japan will run out of gas - and because they lose - you win.
It’s all a widdling factor. Widdle widdle widdle till you win