Why do White people complain about Multiculturalism?

Multiculturalism is meant to divide people even more than its meant to unite, there has always been battles between cultures and tribes throughout history, some tribes doing it for reasons thinking their people and culture are superior to others. No native people ever wanted to give up their culture and nation to foreign immigrants. Look at the Islamic world and Europe, many of them don’t want open borders. The evidence is all over the world, multiculturalism doesn’t work, and immigration is always a problem when it gets out of control. A nation can't stand in diversity, only in unity. Illegal immigration is wrong and is destroying the US, but saying every Hispanic is Mexican and illegal is wrong.