What if my U.S. parent(s) did not register my foreign birth at a U.S. Embassy or Consulate?

If you were born in a foreign country to a U.S. citizen parent or parents and your parent did not register your birth in the form of a Consular Report of Birth FS-240, you may apply to a U.S. passport agency for a U.S. passport (proof of citizenship), or, alternatively, to USCIS for a Certificate of Citizenship to document your U.S. citizenship.