We've done a lousy job of assimilation?
I grew up in an immigrant mill city in Massachusetts; and forgive me if I don't remember the part where everyone else was responsible for immigrants' assimilation. It was generally understood that assimilation was the immigrants' responsibility.
But we supplied the public schools, and emphasized English heavily.
Yes, the PC people have foisted the miss-named "bi-lingual" education on us. But there has been some success to change that, because even the mexican families want their kids to learn english.
Our biggest battle is against liberalism, not against illegal mexicans.