A lot of older people believed in the “magic dirt theory” than anyone will automatically become an American just by touching the soil on our side of the border.
I agree the “magic dirt” theory is nonsense.
That said—it was never given a fair chance.
Imagine if all immigrants (legal or illegal) were required to learn English and pass English tests before they could get any public services (as just one example).
Imagine if all immigrants (legal or illegal) were deported if they were convicted of multiple misdemeanors or a felony.
Imagine if the history and culture taught in public schools focused on the virtues of the country instead of its vices.
There are many other examples.
Leftists have made assimilation (difficult for sure) totally impossible.