It depends upon their parentage. Federal laws have defined who is and is not born a citizen over the last 225 years, but especially in the early years it was based on English Common Law which held that citizenship by birth occurred when a child was born in the country or territories of the country, or when born to parents who were citizens themselves.
If a child does not have to be naturalized, as determined by the law, then they are citizens by birth.
I appreciate your reply. Obviously you have done considerable research on this subject. I confess I have not.
If I understand you correctly, while the plain language of the fourteenth amendment specifies “born in the United States”, legislation has defined that to include a child actually born in another country if that child’s parents were themselves citizens of the United States. I haven’t thought it through completely, but on a practical level, it makes sense.
Thanks again for the explanation.