If the US and British had just waited to send an Army to France the Russians and Nazis would have fought to a severe stalemate. Russia had already defeated a significant Nazi Army by the time the US entered the war. Attrition by both of the engaging armies would have benefited the Brits, French, Eastern Europe, and the US.
Stalin wanted the war in the West, anticipating that the German, French and British armies would bleed each other dry, making the entire continent easy pickings for the Red Army.
It actually was a good thing France fell so quickly, leaving the Germans and English pretty much intact.