I can’t agree with the notion of “mongrels,” they are just people; that has racial overtones.
What IS different is that many, most(?) have less appreciation and history for the Judeo-Christian values and ethics that our nation was founded upon. It is cultural, not racial. And it has been eroded. I don’t know if we can recover.
It is certainly my opinion that those who desire to immigrate legally, take citizenship classes, and wait and sacrifice to get here would tend to be far better Americans than those who don’t.
Sorry to anyone offended.
Also, it refers to those who come into America and deliberately ignore and destroy our principles. This is “mongrelization”, destroying our ideals, thus, our culture.