The Panther and Tiger were susceptible to ambush from the side where the armor was much thinner, though this upgunned British version could penetrate their frontal armor if it managed to shoot first:
General Hatcher claimed that our bridging equipment wasn't strong enough for the heavy tank we had designed. The Germans retreated across intact bridges and then demolished them. We chose instead to use a gun too large for a turret in the open-topped Tank Destroyer, which required infantry support and didn't suit Blitzkrieg assaults but fit Eisenhower's slow, steady approach.
"In part because of the effectiveness of US TD tactics, no German campaign against the US ever achieved its objectives, nor did any TD unit lose more vehicles than its German opponent."
The Bulge area was defended by a thin screen of infantry since we considered it poor tank country. jsw