Well, games are not real life, and have different goals. Nobody is trying to win a victory condition in real life. Civ is a game where only 1 civ can win, and usually that involves being THE dominant power rather than just being a power.
But even in that context, it's pretty clear that size really did matter in WW2. And not just Japan vs America. Despite having a far more advanced military and industrial base, Japan would never manage to subdue China due to it simply being too big even if it was also fighting itself in the meantime. And then you have Germany and Russia. Same thing. It didn't matter how far they pushed or how much they won. It was never winnable to begin with. Russia was simply too big and they could just keep falling back. Certainly if they lost Moscow, the results would be disastrous and many more people would suffer, but the Nazis would never win unless the Russians gave up. Which wasn't happening. Not even Hitler was that delusional.
And of course, Imperial Japan would have fallen apart even without attacking America once America denied them resources. Lack of resources and land was a big deal, which is why they went militaristic in the first place. Pearl Harbor wasn't because they were stupid; it was simple desperation.
Finally, the end of the war just really shows it. All the major Colonial powers lost their colonies, losing land and power. They'd remain strong, but there'd only be 2 superpowers left. Given how biased Civ is towards American history, I think this was probably the intent.