So lets take a scenario here. The United States never enters the war and WWI continues on until 1919 when finally the French mutinies that have dotted the war reach a new and full scale level, essentially couping the government. Philippe Pétain, who supports the coup in the end, takes up the reigns of government as France's new leader. He manages to declare peace and the situation at home settles for a short while.
Then on December 25, 1920 the so called 'Christmas Revolution' breaks out after crackdowns following a bombing of Pétain's Christmas celebration, killing the French leader. With martial law being declared, intense authoritarian laws go into play and several shooting incidents breaking out by troops loyal to the now dead Pétain. When the laws are not let up by the following spring people are getting restless. Finally many unions decide to ally themselves with French anarcho-syndicalist groups and declare a general strike. The troops are ordered in by the government to break up the strikes but they refuse to fire on the civilians and some even join the ranks of the protesters. Soon a full scale civil war breaks out in France. The civil war lasts two years but by 1923 the loyalists (pro-Pétain) have been defeated by the revolutionaries.
Where does France, Europe, and the world go from here? Is an anarcho-syndicalist government established in Paris, or does a more Marxian, Soviet style government come into play? Will two successful communist revolutions now trigger more, in say, Germany, Italy, Spain, or even Britain? How will this effect the cold war in the long run?