I recall another route here, anytime later in the game, assuming the likes of the USA has been successfully shipping units across the Atlantic for a long time while Japan has likewise shipped many many units ashore in Asia, Japan basically builds extra boats and retreats from Asia while advancing en mass to Alaska 20 boatloads per turn for 3 or more turns in a row, some damage to the USA Atlantic transports can ensure nobody gets to quickly come back to stop the mass entrenchment and the Western US factory from becoming a Japanese asset
This looks like the original M&B A&A which I'm more interested in. I can only see the second edition for sale as a computer game. Do you have a link for this one?