Our Germans you mean like Patton? What percentage of our 12 million men under arms were German-Americans?
The cream of the Germany Army and by far the most casualties were suffered at the hands of the Soviets. The greatest battle in terms of size, casualties, and significance was the Battle of Kursk, which dwarfed D-Day. The outnumbered German Army was chewed up by the Soviets who suffered over 20 million casualties during WWII. We didn't kick the German's ass, the Soviets did.
“The German Army in fighting Russia is like an elephant attacking a host of ants. The elephant will kill thousands, perhaps even millions, of ants, but in the end their numbers will overcome him, and he will be eaten to the bone.”
—Colonel Bernd Von Kielst
He said this back when it looked like Barbarossa was going to be a rout for the Germans.
But the Soviets were receiving massive aid from the US that made their victories over the Germans possible. Getting over 100,000 2.5 ton Studebaker trucks from the US certainly improved the mobility of Soviet forces and allowed them to win the battle of Kursk.