U.S. Department of State Foreign Affairs Manual Volume 7 - Consular Affairs
7 FAM 1100 ACQUISITION AND RETENTION OF U.S. CITIZENSHIP AND NATIONALITY
7 FAM 1110 ACQUISITION OF U.S. CITIZENSHIP BY BIRTH IN THE UNITED STATES
(CT:CON-314; 08-21-2009)
(Office of Origin: CA/OCS/PRI)
7 FAM 1111 INTRODUCTION (CT:CON-314; 08-21-2009)
a. U.S. citizenship may be acquired either at birth or through naturalization subsequent to birth. U.S. laws governing the acquisition of citizenship at birth embody two legal principles:
(1) Jus soli (the law of the soil) - a rule of common law under which the place of a person’s birth determines citizenship. In addition to common law, this principle is embodied in the 14th Amendment to the U.S. Constitution and the various U.S. citizenship and nationality statutes.
(2) Jus sanguinis (the law of the bloodline) - a concept of Roman or civil law under which a person’s citizenship is determined by the citizenship of one or both parents. This rule, frequently called citizenship by descent” or “derivative citizenship”, is not embodied in the U.S. Constitution, but such citizenship is granted through statute. As U.S. laws have changed, the requirements for conferring and retaining derivative citizenship have also changed.
“U.S. citizenship may be acquired either at birth or through naturalization subsequent to birth.”
So much for the naturalized AT birth argument. Under American law it is always one or the other - born a citizen or naturalized as a citizen.