And we (ok, though my grandpa´s were in the Wehrmacht I don´t identify myself with the Germany of 1933-45, so I don´t like saying "we") had a 4-fronts war. It´s right, America shouldered much of the burden to defeat Nazi Germany in the West, but it wasn´t the Wehrmacht of 1940, then.
Actually if the Russians and the Germans had not faced off against each other in 1941 and Americans had to invade Europe facing a (relatively) fresh Wehrmacht. We would probably have had our butts handed to us on D-Day.
Of course 3 years later we would have nuked Germany flat when we had enough bombs to do it.