[necovek]

Article touches on this: concept of a nation vs citizenship is a relatively new one (late 18th century with the rise of state-nations).

One can argue the usefulness of any of those distinctions, but there is going to be some genetic and some cultural part to the "nation" definition (around the Balkans, it's been the religion more than anything else to define a nation — like language, I would consider that a cultural component).

You seem to be going strictly for the geographical distinction (with time a contributing factor), but that's in opposition to how nations are defined everywhere (otherwise, it's all Croatians in Croatia today and there wouldn't exist any "Irish Americans", even with Americans being already a mash-up special nation). In Serbian people try to make the distinction by using "Srbi" and "Srbijanci" (citizens), basically Serb vs Serbians, though it is a linguistic stretch (just like we've got Bosniaks/Bošnjaci for a nation to oppose it to Bosnians/Bosanci which includes anyone from Bosnia and Herzegovina).