For example, the vast majority of Europe is now democratic. 200 years ago, most of Europe was autocratic and even exceptions like the UK were at most very incomplete democracies with limited suffrage.

But the constituent nations and ethnicities are very much the same, even though political boundaries have shifted; an English, Polish or Spanish person can read 200 year old texts without much effort. There wasn't any seismic shift comparable to the collapse of the Roman world and the subsequent rearrangement of nations and ethnicities across the continent. Krakow is still Polish, Budapest is still Hungarian and Milan is still Italian.

Only in a few places like Breslau/Wroclaw there was a meaningful population shift.