Unit effectiveness is derived from cost.
Almost every OKW unit is better(especially over time)and costs less or the same as its USF counterpart in one way or another..or in cases like Panther or KT, there is no counterpart.
Why do you think USF gets raped late game? It's not the late tanks. It's the stupid amount of cheap replaceable OP infantry that OKW has thanks to their LACK OF MP BLEED.
The only way to win as USF is contain and wipe the hordes of endless cheap infantry armed with heat seaking rocket launchers(with dirt cheap reinforce) and free LMG miniguns.
Or hope it's a map like Stalingrad.
And you have to do all this containment while being unable to back cap or surround thanks to schewy HQ. And med trucks that take a nuke to destroy with any sort of haste.