Quote Originally Posted by AdamGB View Post
US involvment ended the war quicker, but the Reich was doomed the second operation barbarosa was planned.
Planned? Not sure that's quite true. Certainly by the time they had failed to take Moscow before winter you're right, but the early stages of Barbarosa went very smoothly for the Germans, conceivably it could have kept doing so if it weren't for Hitler making it up as he went along and spreading his army even thinner. Stalingrad was of very little strategic importance for instance, and the German losses there were insane. If those troops had been sent north to help take Moscow initially, things may have been a lot different.
Also, the Americans indirectly had a significant role in that theater. Before PEarl Harbour, Stalin was seriously worried the Japanese would invade Siberia and had much of the red army there. He was able to send them all west to fight at Lenin and Stalingrad once that threat was gone.