If the majority of illegal immigrants were Europeans, this would not be a problem. However, they are mostly coming from Mexico and Central America. For the most part, they are peasants. Every city they amass in turns to crap. Sad but true.
Most liberals/lefties who love the illegal invaders live nowhere near them or move away as quickly as they can when given the chance. Studies show that when whites move, they tend to move to whiter areas. As someone once said, the benefit of a liberal education is acquiring the proper attitudes towards minorities and the means to live far away from them.
Germans create Germanies and Mexicans create Mexicos. This is the problem. They are creating little Mexicos all over the US. Another thing is that they are not easily assimilable. Even if they learn the language, their skin pigmentation prevents them from fully assimilating. This is not just a problem for Mexicans but for Asians, and of course blacks.
They intuitively understand this, which explains why every non-pigmentally assimilable minority in the US has their own pro-ethnic organizations. Sure they claim we're all one race but they throw that out the window when they don't see enough of their race in certain positions, gov't, etc. (This problem would exist in reverse if huge numbers of Europeans invaded China, too.)
In any case, the more multicultural a country is, the more social/racial/economic strife there is. One last thing. Non-Westerners always yap that the US is not multicultural enough. But what about non-white countries? Why is China not whiter? Or India? Or Mexico? Or Africa? Why is it only Western countries that must become more multicultural?