Just imagine for a moment a scenario. Most of the world wakes up to the fact that mixing different peoples in a nation is a terrible idea. Ethno-Nationalism rises, laws are passed, and... All foreigners and descendants thereof are sent back to origin. With compensation when appropriate, such as immigrant owns a house, it's bought back, they keep the money.

It would be hard for them right? Going back "home" when they feel no affiliation to said home. But hey, they or their previous generation did it, plus now they are literally AT HOME.

The country where they had been immigrants returns to glory, as we all know. What about the other countries which get loads of somewhat westernized returned emigrants? Maybe said returnees realize what makes the white country so good, and starts putting pressure for things to change at home. Their nation evolves and is made better.

EVERYBODY WINS.