Consider American Indians born here were not considered citizens until Congress enacted the Indian Citizenship Act in 1924, which granted citizenship to all Native Americans born in the U.S.
Why? Technically, they were considered citizens of their respective tribes, sovereign entities, and subject to those jurisdictions. It didn't matter where they were born, because they were subject to the jurisdiction of the Tribe.
Now, people from another country, citizens of their respective countries are still subject to the jurisdiction of those countries. Congress has passed no law which changes that, nor should it.
Children born to them are, by being children of foreign citizens, are subject to the same jurisdiction as their parents.
The 14th Amendment contains a test, to wit:
All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside.
Those subject to other jurisdictions, as the citizen of a foreign country is, fail the test.
Especially when it is considered that their parents are here illegally.
