US suffered 75,000 casualties in the Battle of the Bulge. It was not the painless slam dunk modern historians try to paint it as being.
The casualty count depends where the line between battles gets drawn. The US Army had been engaged in the inconclusive Battle of the Hurtgen Forest right up until the German attack in the Ardennes.
December 16 is both the end of Hurtgen and the beginning od Ardennes. Really it’s one continuous battle with the Wehrmacht counterattacking just to the south.