Due to the snowy terrain I ruled that vehicles could not exceed their "slow" speed while moving off-road. In addition, the Germans were subject to a "low fuel" rule - each turn a vehicle moved a d6 was rolled. If the result equalled or exceeded the current turn number - no problem. If not, another d6 was rolled and on a "1" the vehicle was out of fuel and immobilized.
At the end of the night the Germans had failed in their mission. I take pretty much full responsibility as the scenario designer for the fact that the game wasn't too close, notwithstanding the dice roll quality disparity. I just gave the Americans too much stuff! For me, the perfect result in a game is one that is decided in the last turn, where momentum ebbs and flows and the outcome is always in doubt. For an "attacker/defender" game like this, the trick is to ensure that the defender is stretched a bit thin and not able to cover every hole adequately. In this game, all Frederick really needed to do was sit in the trenches and let the Germans come to him - he didn't have any really tough decisions to make. If we play again there will be more Germans and fewer GI's. Plus, the Garands rate of fire made every GI shoot like two Germans, which didn't help the balance. Perhaps a change to "5+" marksmanship for the inexperienced GI's? However, in the end I suppose that the Germans didn't win the battle of the Bulge in 1944/45 either, so at least the result was historical ;-)