I won't give a definite no but the was would have waged on for a lot longer and would ha e had a greater chance o ending in a truce. Yes, the Soviet Union did the bulk of the fighting, but they were able to do that fighting because of the trucks and other supplies given to them by the United States. Britain was able to stay in the wake because of the aid given to it by the United States. FDR was backing Britain from the beginning. It would be foolish to believe that the war would Not have turned out very different if the United State had not helped.

Hi OP. This question asks for respondents to speculate, which is against the rules of this sub. As such, I've deleted this post. Do consider x-posting to /r/HistoricalWhatIf; hopefully the creative minds there will take a run at this scenario