The US definitely needs a ton of transports by 1943.
In my current game, they've launched a 30 division Torch and after a while they've just been sitting on some Free French territory outside Marrakesh, barely supplied and unable to counter the 2 Italian cavalry divisions facing them. I've loaded as them and saw that US had 2 transports and but they were still building some medium tanks and a lot of strategic bombers.
I then loaded as Germany, and they completely rule the Atlantic : 10 sub stacks on every sea region between the UK and US no wonder nothing's left floating.