I am an adult education teacher. I had a female student a couple of years ago who was from Laredo, Texas. She told me that her husband was in prison for helping sneak illegal immigrants into the country. She also told me that when she lived on the border, people are allowed to go back and forth to “shop”. She said that when pregnant Mexican women know they are in labor, they take the bus into the US to “shop”. She said they go to a US hospital to have the baby. She said they do this so that when the child is 18, he is a US citizen and can come back here for an education and job.
The idea of persons of "birth right citizenship" who have illegal parents took root in the late 60s. Just being born in the United States was not automatic US citizenship. A perception started to changed in America that came about after Kennedy's immigration 1965 legislation that eliminated the so-called ‘national origin’ quotas, and as usual, the LSM had a large influence. Under the 1940s - 60s 'Bracero' guest worker program, migrant worker's children born in the United States were not deemed US citizens, and when they took their children back to Mexico, no one considered their children US citizens.
There is no court decision or even an executive order that makes illegal immigrants children born in the United States US citizens. All an acquiescence by politicians and with that a change in perception that assumed otherwise. I