What's forgotten is that, back in the day, nearly all immigrants to this nation were coming here to "get rid of their country" and had the desire to assimilate into being an "American". That's not to say that they wanted to rid themselves of their heritage, but rather they were interested in being German-Americans or Italian-Americans. Their aim was to be an America - period. And they also didn't want America to become like te country from which they left or escaped.
Not so with today's Mexican immigrants. They have no interest in assimilation. They want America to conform to them. They aren't necessarily getting rid of their country - just going where the jobs and money are. I personally know of folks who have companies that have Mexican workers that will tell their boss, "Sorry - gotta go back to Mexico for a month or two to be with the family". And they have the expectation their job will be waiting when they get back. I feel pretty certain that 80% of Mexican immigrants have no desire to become "Americans".