> We did fine for a century without any of that.

Did we? I think there's an overly-romanticized view of late 19th and early 20th century immigration to the US. Go to Ellis Island and look at the receiving facilities there where prospective immigrants were evaluated for physical health, mental health, criminal backgrounds, and employment prospects before being admitted into the US. Regardless of how fair or unfair the policies may have been, admittance was not simply open to anyone who showed up on a boat.