Well, let’s not forget that the US was also fighting against Japan for much of that time. And the invasion of occupied France and of Italy was not on easy mode either.

And the collapse of the Wehrmacht on the eastern front had as much to do with the Russian winter, failing supply chains due to non-USSR allied bombing of German factories and railways, and Hitler’s interference in military decisions as it did the accomplishments of the glorious Red Army, which for the first year or more of the invasion, was under-equipped and incompetently led. They learned and adapted, but Stalin’s misguided micromanagement and paranoia cost the USSR hundreds of thousands of soldiers’ and civilian lives.