It is a no-win scenario for the Germans (or at least about 1 out of every 5). They need both luck and score an early win.
Once the American reinforcement kick in for a couple turns, the Germans are done.
Possible fixes: Get rid of the American reinforcement deck. Shorten the number of rounds.
This works well as an introduction to ToI for new players, let the newcomer play the Yanks.
The Germans have some really useless cards like the one that allows an attack on a heavy vehicle.
A relatively easy potential fix would be to starve the US of Command Points. Remove the two US Command Objectives from the entrenchment hexes (they're valuable enough on their own), and turn the generic Command Objective in the building behind the line to a 2-CP or even 1-CP objective. That would limit the US to between 1 and 3 CP per turn, assuming they venture out to hold the hill in the bottom-left corner. They wouldn't easily get a squad every turn, and might even be encouraged to draw more from the Ground Support deck instead since it has cheaper cards. It'd still probably be pretty tough for the Germans, but might at least be an interesting puzzle.
No amphibious attack in history has approached this one in size. Along miles of coastline there were hundreds of vessels and small boats afloat and ant-like files of advancing troops ashore. (Speaking on the Allied landings at Sicily in July 1943)