The trick is NOT to play the Americans.
What you have to play is the Allies, or a member of the Allies.
Trying to do things without your team = loss.
Generally, I go like - Build infantry plus other units in E. US, march them to W. US on next turn, transport to London with transport “A” on next turn, transport to Africa or Europe with transport “B” next turn. It takes a long time to set up a transport chain, but once it’s going as described, it’s a big pain. Especially when you take transport “A” off of shuttle duty and unite it with the rest of the fleet. Five UK transports followed by six US transports is quite a threat.
If you want to go KJF, you build a lotta navy.
Remember, you don’t need to know how to play the AMERICANS. You need to know how to play the ALLIES. It doesn’t matter if you build an Atlantic fleet OR a Pacific fleet if you have the UK doing nothing but building infantry on London, or if you have Moscow buildling nothing but bombers.