The French (cynical opportunists as always) were not really on the side of the Protestants so much as they were opposed to the Catholic Hapsburgs of Spain and Austria. France brutally suppressed the Huguenots, either killing them or driving them from the country, much to the benefit of the lands to which they fled, including England, Prussia, South Africa, the United States, etc.
Yes, these things were really dynastic wars. The Huguenots were allowed to attack Spain and the Spanish colonies during their moment in the sun (they raided villages up and down the coast of Galicia, destroying the church after killing the priest and as many people as they could stuff into the church before they set it on fire). They were pirates in the New World, attacking primarily Spanish territories, but when they were no longer politically expedient, they were dumped.
I’m forever thankful for the revocation of the Edict of Nantes in 1685, without that, I’d be French right now.