Regarding non-white nations excluding whites from immigrating there:
I'd like to see a few million white Christians try to immigrate into any of the following: Saudi Arabia, Turkey, Iran, Syria, Iraq, Indonesia, anywhere in Africa (12 million square miles), Israel (okay- it's pretty small), Vietnam, Thailand, India, Pakistan, Mexico, Central America, Central asia, etc. etc. etc. Don't hold your breath waiting for the entry visas or citizenship applications to be approved. And these are people who would immediately lift the quality of life in such places by a dramatic amount.
I realize that given current demographics and conditions, whites generally don't NEED (because of low birthrates) or WANT (because of their existing high standard of living and quality of life) to emigrate anywhere. But the double standard is clear. All successful white societies are EXPECTED to take in non-whites from across the world, and are called racist if they demur. But nearly all other nations jealously guard their own nations regarding religous and ethnic inflows.
Regarding "asians" not all being part of one race, I'm not talking about classifying people according to scientific methods, or anayzing their DNA. I'm talking about how THEY see themselves, how they are perceived, and how they react to others around them.
Here's the bottom line: one hundred years from now, China, Japan, Africa, Indonesia, the Middle East, Central and South America, etc., will still remain strongholds primarily containing the ethnic/racial groups that currently dominate those regions. Not so regarding North America, Europe and Australia.
Cause for concern? Seems to me it is. Have racial/ethnic groups in the past infiltrated a new region and then acted in concert with their stronghold of origin to annex or dominate new territory? Have such groups ever oppressed the former dominant group of the infiltrated region? Big "yes" to both. Every race or ethnic group has behaved in this way at some point. I just don't want to be on the receiving end, thanks for asking. As a famous historian once said (I think it was A.J.P. Taylor) "History is nothing more than the migration of tribes". Not pretty to be on the receiving end of such migrations, especially when there's resentment that might suddenly turn to ugliness.
Some people don't want to discuss such issues aloud. Why?
They have been discussed for years In America with the same calls that America was being overrun.
First it was the Germans, then the Irish, then the Italians, then the Poles, then the Jews, and now people from Latin America.
History is not on your side about your concern. Your concern has been proven wrong in the last 225 years.
Certainly --- just ask the American Indians --- assimilation doesn't always happen -- sometimes you get pushed onto reservations by the new group who won't assimilate --- they can tell you the dangers of open borders and unlimited immigration and waiting too long to worry about it better than anyone.