Most children born abroad to a U.S. citizen parent(s) acquire U.S. citizenship at birth. As soon as possible after the birth, the U.S. citizen parent(s) should contact the nearest U.S. Embassy or Consulate.
If the consul determines that the child has acquired U.S. citizenship, a consular officer prepares a Consular Report of Birth Abroad of a Citizen of the United States of America (Form FS-240). This document is recognized in the United States as proof of acquisition of U.S. citizenship, and it is acceptable evidence of citizenship for obtaining a passport, entering school, and most other purposes.
Failure to document a child promptly as a U.S. citizen may cause hardship for the parents or child later on when attempting to obtain a passport or register for school. Birth Abroad of a US Citizen
I didn't mean to suggest it was/is your story.
I just know that I don't want the prevaricators to sally forth and retake San Juan Hill on surreptitious American citizenship that shows up PFM-style. (Pretty f*n magic)