Hi Real American:
If you haven't read it, Stalingrad, by Anthony Beevor is a tremendous book. I think you will really enjoy it, if you haven't read it. However, it does show that American aid to the Soviet Union was not overly helpful and did not really turn the tide. We just did not make equiptment for the harsh conditions in Russia and thank God, neither did the Germans. In fact, the great effort of the US, would have been really much harder if the eastern front was not held and collapsing from the extrodinary efforts of the Soviet Red Army. Now, one may argue that without Stalinist purges and such, the Red Army could have been putting more into fighting the Germans, however, on the other hand, it is hard to second guess history, the reality, is unlike France and Poland and so many others, Russians did not capitulate.
all the best
Larry