What's so great about racially homogenous societies? Are you inferring that as countries and societies become more diverse their culture is threatened?
First of all, Asian societies are notoriously racist - the Chinese hate the Vietnamese, the Japanese hate the Chinese, the Lao hate the Thai ... so why would any society want to emulate that?
As for the Middle East, it is NOT almost 100% Arab as you say. Much of the Middle East is populated by Africans and the descendents of Africans. As for the Iranians and the Kurds, they're not Arabs, they're Indo-Europeans.
"Just because a few europeans killed the native indians, etc doesn't mean the whole race has to be punished." - What the hell does that mean? Who is "punishing" the Europeans? Immigrants? What a bunch of racist crap.
And since when has European culture been threatened? Please. While it is true that Europe and other liberal societies are having to deal with certain, regrettable social customs amongst some immigrants (female circumcision, honor killings, etc.), the vast majority of immigrants become productive members of society. If we really care about the preservation of culture, then we have to respect other cultures and promote secular democracy, not racial segregation as you seem to be suggesting.
Frankly, I'll be happy when international borders (which are pretty porous anyway) are broken down and people are allowed to immigrate wherever they want.