>Moving to a different country, with a different language, political structure, culture, history etc. cannot be compared with migration within a country.

It is way more similar Sweden to Norway than California to Florida.

> also in a completely different language region.

Not really. The laguage is different but very similar as countries share history and until a hundred years ago any village would have been able to talk to all the villages around it indepdendenly of which country they were in. Language changed gradually from village to village.

Any Spanish speaker can read many words and sentences in French, Italian or Romanian as they share much in common. Swedish and English have a lot in common, Spanish and Portuguese the same, Norwegian and Swedish are extremely similar like Danish (even that nobody really understand the Danish when they speak).

Even culture in the South of Spain is more similar to the one in the North of Africa than to the one in the North of Europe, as there is shared history and both are Mediterranean locations.

In my view, Chinese and French are really completely different. Finnish and Swedish are completely different, even that they are phisically very close (but many Finnish people speaks Swedish because again they live close by).

Countries are administrative regions for legal purposes, but culture is more permeable than that.

You are right that migration between countries means something, I just think that it is misleading in many cases at least in Europe (and probably other parts of the world) as there is a strong shared history.