So what, multiculturalism isn't any better. In America and western Europe, they're fragmented culturally as more people from different cultures try to conglomerate in one area.

Where is the evidence that multiculturalism works? Look at Rome. During the decades before its collapse Barbarians immigrated into the empire attracted by its wealth and economy. The Romans had grown complacent and out of touch with the threat that the foreign Barbarian culture posed, they assumed they shared Roman values and were no major threat. Until one particularly harsh winter forced tens of thousands of Barbarians south into Roman territory. These Barbarians sacked Roman cities for years before reaching Rome itself. Their migration brought the entire empire to a collapse.
The longest lasting nations are nationalistic, they are skeptical of outsiders, and they rely on a unified culture to bring them through tough times. An example of these nations are Russia and China.

There is no evidence that mixing people with different moral and cultural beliefs, with different languages and customs, with different views on law and order is advantageous to a nation. It's like thinking you will do better on a group project if you work in a diverse group with a kid that doesn't speak English, another that thinks every aspect of the project needs to be justified by God, and a third that is adamant about limiting the report to a single page to save paper.

Personally I would rather violently remove any foreigners from Asia violently. White or black they should stay where they come from. How the current Filipino president Duterte deals with drug dealers by blood, is how you deal with sexpats or foreigners to get them out your country.