The issue lies with the stratagem of each faction.
The Americans require far more finesse than the two Axis factions, who's motto is, comparatively, 'I POINT THIS HUGE METAL THING AT YOU YOU DIE NAOW!!!'
With the USF, you can fend off Axis armor, but you basically need at least 4 ATGs on the field at a time, paired up in a buddy system, in order to achieve the same overmatching "F OFF" effect--unless you have a pair of them with APDS rounds popped, any Axis vehicle that's not a 222, StuG, or Puma will simply drive up to you and derp the crew. With a pair of ATGs, and, hopefully the Captain (quickly becoming one of my most favorite units), you can force them off.
The issue then becomes fending off the inevitable Ober horde; unless you have a 2:1 ratio of dual LMG'd Rifles/AB present for each Ober, you won't be able to force them off and retain enough bodies to meatshield a second attack (assuming you don't have a Doge [
] ambulance nearby).