Stating an extreme opposite and obviously false position on something to sarcastically attack a true position is the customary rhetorical method of fascists such as both Hitler and "Guest, Stalin".

It's an avoidance of actual dialogue.

Here's how I break it down for defeating the Nazis:

Great Britain: 30% credit
Soviet Union: 40% credit
America: 30% credit

The only reason I give the British as much credit as the USA is this: They fought alone from the time of the fall of France until June of '41, and they held off the Germans at the height of their power and saved the West. Had England not held in 1940, the Germans would have been untouchable in Western Europe, and the USA would have had to settle for co-existing with a German-controlled Europe while the Germans fought a long, bitter war in Russia...which they might or might not have won in the end. My guess is, the Russians and Germans would have fought to a stalemate, had England fallen.

The USA and Germany would then have glowered at each other across the Atlantic for some considerable time afterward, but probably not fought a direct war with one another, because neither one of them could have effectively mounted an invasion of the other across that ocean. Too big a logistical challenge.

Most likely they would have settled for limited military squabbles and interventions here and there in places like Africa and the Middle East. A kind of "cold war", in other words, similar to what developed between the Soviets and the Americans after WWII.

Russia would have suffered terribly, but probably have held out with some loss of the westernmost areas to the Germans.

As for Japan, that's a separate matter. The Americans would undoubtedly have fought Japan anyway in '41, and defeated them by '45, due to vastly outproducing them in armaments.