It is true that 9 of 10 Germans were killed by the Red Army, but the Russians killed essentially no Japanese or Italians in combat.
The Russians could not have defeated the Germans without our alliance, but equally we could not have defeated them without either Russian alliance or a far greater number of casualties.
What many don't realize is that the true second front in Europe starting from 42 was in the air over Germany. Aside from turning Germany into a pigpen from end to end, the air war absorbed something like half of Germany's production of heavy guns (for AA) which otherwise would have been available for the Eastern front.
Once we got the A-Bomb in the summer of '45, if we had been fighting Germany alone, we would have started dropping 'em all over the Fatherland and that would have ended the war with Germany as quickly as the war with Japan was ended.
Similarly, the Russians escaped German annihilation when Barbarossa was postponed by a few weeks which pushed forward the German invasion into the winter months which had defeated other like Napoleon before. This fortuitous postponement was courtesy of the Yugoslavs or Serbs who said up yours to Hitler and got rid of quislings when told to capitulate which enraged Hitler and made him decide to go after the Serbs first - a significant blunder.
The Americans came late into the war but without that support and entry by the USA and then the Russians to back Britain, the Germans could have eventually won and made the world a rotten place to live in. It took four years for the rest of the world or Allies to defeat the Germans and then stop Japan courtesy of nukes. One has to look with respect at the fighting spirit and organization of the Krauts and the Japs which required the rest of the world four years to defeat these two enemy countries. But without the U.S., the remaining Allies would have been toast in WW-2.
Hitler is stated to have observed that FDR was a National Socialist like the Nazis but despite having come to power at around the same time as Hitler, FDR did not accomplish what Hitler had accomplished. Hitler felt FDR was jealous!! Of course Hitler used his Secret Army (formed and led by a bunch of blatant homosexuals and perverts who were its generals and officers), then the Secret Service and the Gestapo to achieve his aims by force. Interesting to see that Hitler acknowledges that the U.S. Democrats subscribe to Nazism.
The only rotten thing in the Allied victory was that Stalin was the only other powerful dictator with Hitler gone. We know what a mess the commies inflicted later on world peace for the next fifty years. Should have gone after Stalin too in 1945.
If Germany had defeated Russia in World War II just as Germany defeated Russia in World War I, Germany would still have lost the war and the U.S. would have still kept casualties relatively low.
The difference is that V.E. day would have been in late 1945 and that Berlin instead of Nagasaki would now be used in the same sentence with Hiroshima.