I got my butt kicked as Japan the first few times I played, and it was horrible. If you take two new players of equal but very low skill just learning the game, the person playing America has a very decisive advantage over the person playing Japan. America has a lot of built in safety nets. You are the aggressor, you have a ton of money to throw at the problem, and you have very focused objectives such as “build a big ass army/navy and go stomp on something”. When you are just learning to play the game, that kind of macro-thinking can easily win and we as a group thought things like “how can you possibly beat America”
Learning to play Japan means learning tactics like moving Japan’s production out of Japan, always building the IJN (even if it’s just a submarine), investing in facilities early, keeping your fleet in counterattack range of vital targets at all times, maintaining the DEI, cutting off India/China without having to waste resources conquering them, how to utilize Japan’s massive air force effectively, and so on and so on.
Now when we play America and you realize all of the faults of America, it can feel hopeless going up against a Japan that’s making 70+ IPC, no Chinese left, and India making like 7 IPC a turn with a bombed out factory and no navy. Then it’s just you and tiny little Anzac against an opponent that can build defenses to anything you build two turns before you can even get it there and you have Britain and Russia begging you spend money you don’t have on the other side of the world.
I think it’s just the natural curve of the game.