If a baby is born in the US, How will it become a Citizen?
Does one of the parents need to be a Citizen? Which one?
Should EVERYONE born in the US NOT be automatically be a US citizen?
Should Citizenship be granted to people who are only here legally?
What if a couple is here with a legal Tourist visa and they have a baby here?
If the idea of ending Birth-Right Citizenship is being floated, the propopnents of the damn thing had better put on their thinking hats for this one...
Leaving aside the question as to whether "Birthright" citizenship can be changed without changing the constitution, the US would have to develop an "American nationality law" governing the acquisition and transmission of American citizenship.
Here is an article on Germany's nationality law. It gives an example of the types of considerations that are important in such a law. Also note that it is a law that has been re-formulated/changed over time.
https://en.wikipedia.org/wiki/German_nationality_law