There is no cost-effective counter to allied infantry blobs,no amount of romanticism will change this fact.
Yes there is. Just important is to use it well. Sadly as axis you will sweat more than allies.
Vs USA it's good to make a flak HT cover by AT guns(but you must make them really fast after flak) and use it defensivly. Green cover all the time, use sturmpio when enemy is focusing your other units, kubel in early game helps a lot and most of all remember not to split your forces too much
But definitely it all depends on who's USA teammate.
And do not blob!