Years ago I was talking history with a colleague from Germany, and made a similar comment:
"We kicked your ass twice!" (it was said in a joking way, not as an insult)
His retort: "Ya, this is true. But it took ze whole vorld to do it!"
I think it was pretty much US manufacturing and Russian bodies. And that was with the US and Brits simultaneously fighting the Japanese. OTOH, my uncles were in the European theater and did credit the Germans as the best soldiers (not sure, maybe they meant the best soldiers of the Axis).