Before the breakup of the Soviet Union, Estonia had been a nation state for 21 years in total, from 1918 until 1939. Before that it had been part of the Russian Empire, East Prussia, a Lithuanian-Polish confederacy, and Sweden, among others, as a region with significant linguistic, cultural, and ethnic heritage of its own. So a bit like Catalunya is today. Or a bit like Kosovo, which is primarily ethnic Albanian, whereas Serbia is, well, Serbian, as I'm sure you know.
Ireland hadn't been independent in 800 years before 1922.
Nations have always emerged and disappeared. Deciding whether a people have the right to self-determination based on whether or not they was a Grand Duchy with significant autonomy in that region in 1722 isn't exactly the best way of going about things.
Again, the potential for things to be less than perfectly clean isn't the best reason for keeping Catalunya part of Spain. The path to an independent Catalunya, if that's what significant proportions of the people in the region wanted, would probably involve very complicated negotiations about which regions stayed in Spain, which stayed in France, and which wanted to join the Catalan Republic, or whatever they called it. The fact that Perpignan might well choose of their own free will to remain part of France shouldn't be a deal-breaker for secession of other regions from Spain, in the same way that the choice of the Six Counties to remain part of the UK shouldn't have meant that Galway, Cork, and Tipperary should have their wish for independence ignored.Even if votes were permitted, the other issue is that it's not simplythe Spanish side of the regionBarcelona's decision to make. The rest of Catalonia seems quite happy living in France and Spain.
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