I seriously doubt the 90% losses in the USSR for a few reasons: The figure given for staffing difference was one soldier in the west for every four in Russia, the war in Russia started later than other theaters (France, North Africa, Balkans), and a year before Normandy the Germans were responsible for defending Italy itself (and did so until the end of the war). Also, plenty of Ukrainians joined the war against Stalin, so those “Soviet” losses shouldn’t be tallied in the same manner.
The Soviets paid the price in blood fighting a former ally they helped arm, and who cooperated with them in the division of Eastern Europe early in the war (invading Poland and the Baltic states from the east). There was nothing praiseworthy in them having to defend themselves against a monster they helped create; before hostilities they helped the Germans develop weapons and train pilots to evade the eyes of Versailles Treaty inspectors (that is why some of their plane designs were similar).
Germany was a continental powerhouse with no global war capabilities; regardless of the eastern Front, they had no way of defeating the Allies. Britain had an empire to bring to bear against them, and they couldn’t harm US interests in any meaningful way.
It required the combined resources of the United States, the British Empire and the Soviet Union to defeat German in Europe.
It is true there was no way German could defeat the United States. However, without war in the Soviet Union, the probability of making in significant inroads in Western Europe until sometime after mid 1945 would have been problematic at best. Highly doubtful that there would have been a D day 1944.