Don't believe everything you read.
I have contact with many immigrants every day, at least if I leave the house, and that was even true in the backwoods of West Virginia. My first cousin married someone from Puerto Rico over 50 years ago. There are gravestones fifty feet from where my parents and grandparents are buried with inscriptions in Arabic. I had neighbors who were from Italy. That's what America is.
I like most of the immigrants. On the whole, they are much easier to deal with than many native born (though not native Americans) people I sometimes deal with, who can be arrogant, lazy, prone to violence and drinking, scofflaws and often have a poor command of English, although I will concede, they are not English. My wife, an elementary school teacher, has a slightly different opinion. She had children whose parents are illiterate in English and sometimes cannot yet speak English, although they are just as often illiterate in Spanish, too, which is the language of many of her students, though by no means the majority.
I don't know where all these millions are coming from but there must surely be parts of the world that are becoming depopulated. I know that is the case where I'm from and I guess I'm part of the reason why.
You know that the whole idea of citizenship doesn't go back all that far but it was a long time before American Indians were granted citizenship.