It's my opinion, by the way, that no one country acting alone could have defeated the Germans in a land war in western and central Europe after their lopsided victory in the Battle of France. The English certainly could not have done it alone. The USA could not have done it alone either...they needed the UK as a staging ground for fullscale invasion of Europe, and they needed the Russians to tie down 3/4 of the German army for them.

The Russians might have been able to defeat the Germans alone...in a very long war of attrition...but I doubt it. I think more likely that it would have ended in a stalemate or that the Germans would have won such a conflict.

And to look at it from the other angle...the Germans could not have defeated the USA or Great Britain either, simply because the Germans lacked a big enough navy to project their formidable army across either the English Channel or the Atlantic. They also lacked the kind of large strategic bomber aircraft needed to wage a really effective strategic bombing campaign that could cripple an opponent's industrial base.

The only people in WWII who had such aircraft in large numbers were the British and the Americans. Those aircraft were the B-17, the Lancaster, the Halifax, the Stirling, and the B-24.

Germany's He 111s, Ju 88s, and Dornier 17s were not 4 engine strategic bombers, they were 2 engine tactical bombers, and they were not up to the task of waging a strategic bombing campaign. The Russians, likewise, lacked such capability, having an almost entirely tactical airforce suited to close support on the battlefield.