I have to agree that to get a Communist France as of 1939, you need a POD long before, probably one that changes global perceptions a bit as to what the Communists were all about--not enough to prevent right-wing opponents from seeing them as the Devil on Earth of course, but enough that left-wing people are more willing to unite behind their banner. That probably does require much less of a perception that the various national parties are in fact tools of Moscow. Anyway if we have Communist run France in 1938, it probably did not happen by means of peaceful elections alone--elections probably did have to go better for them sooner than in OTL, but they will not be allowed to take power peacefully. In the course of the struggle to take over Paris, I daresay all of Europe would be thrown into convulsions. France will have lost control of all colonies; I would think that some faction would claim to be the legitimate French government in exile and this lot would be supported to run the colonies by Britain. The government in exile would have rather more manpower than just the French colonists plus emigre military; a substantial number of French citizens would be emigres.
Whether Algeria would be under Parisian Communist control or not, would depend on whether the Reds were strong there or not, but given the basic politics of the colony I'd assume no, they are on the White side and probably the seat of the government in exile.
Whether France is seen as the leading military power in Europe as OTL (until the Battle of France that is) depends on how badly the revolutionary war period damages the country, on what proportions the Army, Navy and other forces split up with, and how much latitude the new government has at rebuilding.
The diplomatic map of all Europe will be completely shaken up by this event.
And no, Hitler cannot contemplate attacking the USSR without conquering France first--as in OTL he will need to steal that country's resources, never mind he can't have them at his back. Will Stalin stand foursquare against a Reich attack on France? I could argue either way! But possibly a necessary condition for France to be Communist might be to butterfly away Stalin's rule of the Soviet Union anyway!