The Americans have two times more squads with a lot of specialization and plenty of time. Maybe cutting 1-2 turns will make it more challenging.
This scenario is fun for the US; the Germans don't have much to do but shoot and die.
It's pretty much a one-way street. There's a certain amount you can do as defender, but the Americans are just too numerous for this to be even remotely fair.
The Americans win quite comfortably. Recommendations: cutting the time to 6 rounds, remove "Take down the beast" strategy card from German deck (they're completely useless) and perhaps remove some American half-tracks.
"A good scenario."
Favors: Americans+
Fixes:
(a) Maybe cutting 1-2 turns will make it more challenging.
(b) give the Germans 2 extra infantry squads (c) Removing the American half-tracks might balance it better (the reinforcements can arrive in transport, that's fine).