It would have ended with a German loss no matter what once the US committed.

The Russian factories were cranking out trucks, tanks, planes, etc, and they had the personnel numbers, not to mention the "lend lease" supplies the US was providing. Don't think the Germans would have been able to prevent the Russians steamrolling them. The Russians would have lost a lot more lives, but with the Germans having to keep troops in France (to prevent a second D-Day attempt), as well as the US and British forces coming up from Italy... Nope, the Germans weren't going to win, nor have anything short of a full, unconditional surrender. But I do agree with Sarah that if Hitler had just stopped after their first few acquisitions (before heading into Poland), they wouldn't have had to worry about the Allies. The US still held an isolationist view of the world, and Stalin would have been perfectly happy to stay within his borders...at least at that time. Russia probably would have moved a significant portion of their forces to their eastern border after Japan invaded Manchuria. If Hitler hadn't made any further advances, Neville Chamberlain was perfectly happy to appease Hitler's acquisitions. And we saw how quickly France fell (with Brit troops), they wouldn't have posed a serious threat to the Germans.

consolidating, but the hubris caused him to go too fast and get overextended. Not that I root for him, ha.