At least Germany, Spain, Italy, France have evolved from a myriad of city states, duchy, great fief, that have been unified, conquered, inherited, etc to form a bigger central power.
European separatist movement are usually basing their claims on these previous historical divisions (Catalonia, Brittany, Scotland...)
- This historical countries have different languages. (Euskera, Galician, Catalonian) - This countries are different than other "Autonomous communities" in terms of primary sectors.
Sometimes the Spain government not accept some particular things that happens in this historic countries, plus we come from 39 years of dictatorial state where our languages were banned. Nowadays this historical countries are promoting these languages + spanish, but Spain government didn't accept that.
One of my grandfather got shot for speaking in Galician, another got political asylum in Netherlands after cross the Portuguese border, my family fight for our culture, I want to keep that. I'm spanish but I'm speaking different language, I have different habits, I don't want to be independent but I want that Spanish government try to understand that we are a bit different, only that..
Meanwhile Spain government keeps shot old historic regions and try to kill their culture, Spain will have a problem. Nowadays Catalunya problem it's huge for Spain, and Spain government didn't do anything about and this is too sad :-(
They spoke the same language, it was basically happening in the context of feudal system which was from the point of view of the operations of government modular - basically the whole political system supported pretty well constant shifting of the ruling body - I kneel to you, they kneel to me, and I give you some grain and provide men in time of war. And ruling was pretty simple back then.
Before 1600:s the function of government was basically the king. After they figured out there must be a better way to rule than riding ones bottom sore ruling and taxing about modern state functions began to emerge. I believe this was at the time of Gustavus Adolphus II in sweden (https://en.wikipedia.org/wiki/Gustavus_Adolphus_of_Sweden).