Plus it'd be pretty hard to be an oppressive dictatorship (looking at you, California) if the people could just up and move to a less oppressive regime (like Arizona). Of course I'm (mostly) joking with my example but a CA->AZ mass migration is happening as we speak and nobody is calling for a wall on the border (yet). They can't put up massive apartment/condo monstrosities fast enough to handle all the new folks moving here and presumably they're finding jobs without too much trouble.
So, yeah, I think if governments had to compete to retain their "subjects" the world would be a much better place and people probably wouldn't need to relocate unless they really wanted to unlike today's multiple "migration crises" (their term, not mine).
There's a difference between displacing the local population (which you imply) and moving somewhere there's better opportunities (jobs, housing, &etc). As long as there's no coercion or violence involved then who's the victim if my new neighbor is from Guatemala?
Sounds fine, but what happens in the scenarios I actually outlined in my first post? It’s not about displacement, but simple overwhelming numbers. Would Japan still be Japan if tens of millions of people from all around the world decided to live there? Would Albania still be Albania if a hundred million people from China and India showed up? If everyone in California were suddenly matched 3:1 by Sub-Saharan Africans, what happens?
In terms of language, culture, social services, law enforcement, etc... you’re suddenly in a whole new world. I don’t necessarily think it’s wrong for Japan, to use a precious example, to wish to remain Japanese in terms of their language and culture. I don’t think it’s wrong for Switzerland to balk at the notion of a hundred million Americans showing up either.
If you remove all restrictions, it’s not just about having a Guatemalan neighbor; that’s just immigration as it is today. The US for example has absorbed millions of Mexicans, Central and South Americans without any real problems. It is after all, a drop the proverbial bucket. The issue arises when it’s far more than that, order of magnitude more, and all at once.
What would happen to Guatemala if a sizeable chunk of the US, or China, India, or Africa immigrated there? It would implode, socially, financially, and its existing culture would be consumed. If everyone who wanted to live in Hawaii or Monaco could just move there, both places would be environmentally and economically trashed. Immigration is necessary and human, and there should be more of it in most cases than we see today. That doesn’t imply that total freedom of movement is workable or desirable either. I’d no more want to live in a country with no immigration limits, than I would in a country with no immigration; both would be broken.