My son went to a boarding school that was heavily populated with the children of rich people from Mexico, Central and South America. We thought of it as an "international" environment--boy, did we sure learn quickly that the culture that these kids brought with them was saturated with sadism and cruelty. These were rich kids whose parents didn't want them hanging around because: (a) they were a pain-in-the-neck to the dad's mistress; (b) they were at risk of being kidnapped because dad was so rich; or, (c) they were at risk because dad was really a drug don and his kids were targets of rival drug kingpins. The rule of the school was that you couldn't carry more than $20 with you--so they carried 20 $100 bills. You weren't supposed to speak anything but English (to improve their skills for "international business"), but they constantly spoke Spanish and bullied those around them into compliance. Worst of all, the punishments they inflicted upon boys who were somehow weaker than they were thoughtfully sadistic and planned with precision.
As a country, we have had a brutal history of conflict between races and ethnicities. However, the absolute evil of these people streaming into the country today will make the horrors of the past look like child's play.