Actually, America had been an industrial power for a bit of time at this point. They won WWI the same way. Then after that, the twenties came and went, in which there was too much surplus, and the market crashed. In the late thirties, we ended the depression by producing supplies for Britain. We were still producing consumer goods.
Then, after Pearl Harbor, our massive industrial strength shifted, to military purposes, and Japan was not going to win the war unless they managed to keep more carriers than us.
The reason, of course for our massive industry is our unbombability and population size.