I’ll take your thought and restate it.
It’s like the second law of thermodynamics.... Population flows from poorer regions to richer regions. Never the reverse
The influx be it slow or rapid, causes governments to adjust and even fail.
The wealth of North America and Europe is producing a population flow from the poor hinderlands to the south.
You have a good point regarding the influx of poorer people into the U.S., but there’s more to it than just that. I’m referring to the attitudes I find even among middle-class and upper-class people.