Playing the USA is a bit tricky. It’s really a different situation based on how the Axis go about things (mostly with Japan, if they go for a straight takeover of china, or going for dutch, etc.)
I’ve noticed that especially if you do the 1936 setup, that it’s important that the USA focuses it’s early turns on ground forces. The factories can keep up no problem earlier on, and it starts with an OK navy. Later when they start making more, they can easily build up transports, and be ready to throw it’s forces in right away when the war starts, especially if the Atlantic is under control.
I’ve noticed otherwise that it’s hard to compete with the Japanese navy, especially if the campaigns are going well for them in China and other places. I’ve started coordinating with England to put a large part of their overall navy into the pacific to really put a dent into their forces in order for the USA to finish them off well.
That’s what I’ve gotten to understand from the few games that I’ve played.