What would happen in an alternate universe where Turkey has a revolution of the people and joins the CCCP?
Well, the whole world goes crazy. I declare one little war on tiny Bulgaria to grab its IC and everybody goes insane! Greece and Romania jump in on it against me, apparently threatened by communism despite our good relations and non-aggression pacts. Greece actually briefly occupied Izmir and Istanbul before friendly CCCP forces arrived from the Caucasus. Yugoslavia also tried to get a piece of the action, but squirrels out peace treaty with the CCCP after a few of my divisions invade them as Bulgaria and Greece fall. I let their limp-wristedness slide, since Poland(!) and Romania have joined the Axis and the Germans make a successful amphibious assault on Leningrad and rapidly march south, making it all the way to the gates of Moscow. Alas, my brethren sent me far too many units and almost suffered a catastrophic defeat because of it. Fortunately the Germans also devoted a number to defend their Romanian allies.
Hungary declares against me without joining the Axis. Czechoslovakia also stays neutral re: the Axis, as well as the Comintern, but declares war on Australia, prompting French bombers to make passes on them from captured airbases in south Germany. Italy makes several good beachheads in Peloponnesia but are eventually driven back to the sea by my Russian comrades. Meanwhile, the French capture the entirety of mainland Italy and I eliminate Romania and reconnect with my communist brethren as I crush Axis forces from behind in late '37. We are now poised to launch a tremendous counter-offensive in 1938, and my veteran divisions, organized mostly into general-commanded armies, should easily crush the highly organized but often outnumbered Axis forces.
EDIT: UPDATE: The Iron Curtain has fallen ten years prematurely with the creation of a stalinist DDR and Poland. Hungary is poised to be devoured, as is Yugoslavia.