We have the same thing going on in Europe and to be fair I don't know what stance I should take. I think this is a very hard topic and there are no right choices.
Countries that don't enforce their borders tend to get subsumed. That is true historically and, because of human nature, seems like it will remain the case.
A more-detailed analysis with respect to modern Europe:
The Strange Death of Europe, by Murray
https://a.co/d/ap02d6DMy feeling is that there are regions that once had great vigor. Where people had the fire to thrive and populate their lands. But now whose people have become diffident, with vigor drained away. They are like the Elves in the Lord of the Rings. No more fire for such things. They receded and faded away. The land went to those who still had desire to thrive, to move in, to populate, and to take over.
I am hoping Europeans don't go the way of the Elves.