The Citizenship Clause of the 14th Amendment guarantees citizenship to any baby born in the United States, with one proviso: you have to be "subject to the jurisdiction thereof". The issue is over whether a baby born to illegal alien parents is subject to U.S. jurisdiction. One argument is that since a person within the United States is covered by the law generally, he is so "subject" and so is a citizen. OTOH, Senator Jacob Howard, who had authored the Citizenship Clause, said that they babies born in the United States of foreigners are not covered by that clause, because their allegiance is to the country of their parents and not to the United States.
The Supreme Court has interpreted the Citizenship Clause multiple times, but never this situation. President Trump's executive order would likely force the issue into the Supreme Court, because there will be Liberal federal judges who will strike it down. This issue could be before the Supreme Court in time for the 2020 campaign.
It seemed to be consistent with the 14th.
Congress defined part of the understanding of the 14th a hundred years ago, making Native Americans citizens not just members of their tribes.