Russia/Germany were already neutral allies and Russia was already supplying Germany with resources at the time. Russia would have sided with Germany before they ever sided with the United States....Invading Russia was a huge strategic error...Even if Russia stayed neutral it would have drawn out the war with Germany efforts focused on fighting one front which would have meant the first atomic bomb drop would have went to Germany, rewriting history. Not only this but would have gave birth to many other of Germany's superior armory advancements.