Yes, there were other units of the US army involved in fighting the Germans besides those who were sent to Bastogne, like those who were already in place on the western wall.
Not much history written about those early days of The Bulge and the delaying action, for some reason...
I think the German advance in the “Bulge” was halted partly by lack of fuel and also bridges being blown.
I know the German commander was quoted as saying something like, “they would have succeeded if not for those damned engineers.”