Trump could end birthright citizenship on day one of his new administration. Currently, under US law, a person is granted US citizenship if they're born in the country, even if both parents are here illegally. Trump previously announced a day one policy to end this.
Trump is arguing that birthright citizenship creates an incentive for illegal immigration. If a child can be born on American soil, it opens the door to various social benefits and chain migration, where they can bring in their family members.
https://gettr.com/post/p3dipe3778e
