Now, let's say that France suffers a crushing defeat against the Germans in WWI enough to destabilize the government and give traction to communist revolutionaries. I know it's always a question of 'how' they lose, so in this case let's say that the US stays neutral due to better diplomacy on the part of Berlin. The war drags on to late 1919, say, with France suing for peace and losing Briey and the surrounding area as well as paying massive war indemnities. The unpopularity of this loss causes a communist revolution, which eventually succeeds in establishing a communist government in Paris in... phwoar, 1922?
The reason Germany and Britain do not intervene here is largely due to the former putting out revolts and consolidating their rule in the east after an exhaustive war and the latter struggling against it's own internal troubles -though Britain won't see nearly as much trouble as France due to not actually losing any territory in the war-. Though perhaps reactionary fascism gets a political boost. In any event, they're not important here.
In part because of the German U-boat campaign strangling coal shipments and plunging the Spanish economy into recession compounded with preexisting factors Spain destabilises and tumults into civil war in the mid-1920s, egged on by French actors. They to establish a communist government just shy of 1930.
Now, my question is, is there any chance of a union between Spain and France presuming international communism is popular in both? The extent of which can vary from a monetary union, something as simple -and dull- as a defence pact, to outright political union. Feel free to pick holes in my scenario, but I'd like the question in particular answered if that's alright.