American media sources seem to generally refer to Anwar al-Awlaki as “U.S.-born” (PBS; NBC; CNN) rather than as a “U.S. citizen.”
I'm just curious whether legally there is any ambiguity in al-Awlaki's citizenship status (at the time of his death), or if the media is just avoiding stating that directly. I can't find anything to suggest that his citizenship was revoked through some legal process, or that he renounced it. (Perhaps certain actions can get your citizenship revoked automatically?)