Consider that, globally, Japan will never have to conquer the US. You act as if that should be achievable. Japan, conquering the US. That would be, and should be, impossible unless the US messes up big time. Japan’s goal with the US is to keep him bottled up and waste resources that should be going to Europe so Germany can push into Russia.
How do all of your Axis and Allies games end? The reason one side gives up is because this outcome is inevitable by the game’s conclusion, due to the economic swing. In AA50, if Japan gets all her NOs and most of Asia you’re looking at a 65+ IPC monster against a maybe 40 IPC US. If Japan didn’t screw up too badly in taking all of Asia and still has a sizeable portion of her fleet intact, there’s no way the US can win, barring the dice roll of the century. It’s simple economics, as those extra 25 IPCs a turn add up to a likely victory. It’s even more apparent in AA50 since the US has to split those 40 IPCs to DEFEND both Eastern and Western USA against German/Italian AND Japanese fleets by Axis end-game.
However, America ISN’T in this game going to be threatened by Germany, whereas Japan has at least two fronts going for it (India, Aus, AND the US). I assume if the Japan player is smart they’ll nip India in the bud as early as possible while the US isn’t in the war. But even with most of her NOs nearly taken, how is Japan supposed to compete againt a a one-front USA?