20% of the whole population are immigrants. In the big cities, where problems are worst, it is far higher than that.

I can't respond to your point about problems in big cities, since you don't specify what they are, but rural areas have a whole host of problems that cities don't face, so I'm gonna need more than a vague assertion.

Though it still won't help your argument, because 1) correlation != causation, and 2) there are literally thousands of comparable correlations, so why is it immigrants, and not any of the others?