Illegal immigration also drives down wages for American workers, both skilled and unskilled.
No it doesn't. Most illegal workers are pretty well organized and know their rights.
They usually get at least minimum wage.
The few sweat shops exploiting workers are not long lived and have been and will be found out.
And, a lot of Americans don't want to do the low level work that illegals perform. (harvest, cleaning, landscaping, construction)
Lastly, let's face that not everybody has the brains to be brilliant. Too many people in the world with low level intelligence.
Unfortunately these people seem to reproduce the most making more and more unneeded people.