Are we just going to ignore the Molotov–Ribbentrop Pact, wherein Stalin let Hitler invade Poland as long as he got half of Poland, Lithuania, and Estonia?
You know what the US never did? Call Hilter and agree to a joint imperialist effort in carving up sovereign nations.
Edit:
“there is one common element in the ideology of Germany, Italy, and the Soviet Union: opposition to the capitalist democracies” or that “it seems to us rather unnatural that a socialist state would stand on the side of the western democracies”.