It has nothing to do with US Citizens. According to estimates from the Pew Research Center and the Center for Migration Studies, roughly 250,000 to 400,000 children are born each year in the U.S. to undocumented immigrants, virtually all of whom receive citizenship at birth under the 14th Amendment. The underlying issue is the exploitation of a legal loophole that currently incentivizes unlawful entry and exploitation.
https://www.pewresearch.org/race-and-ethnicity/2015/09/28/mo...