I may be mistaken because this is based on old information, but: to be a legitimate marriage, the American must first obtain a certificate of eligibility to marry at the US embassy. If he/she has it, and if the marriage is conducted by a person legally authorized to marry, then it automatically enters the NSA records. How the USA finds out that the marriage actually occurred, I have no idea, but they don't seem to know until the newly married apply for a temporary resident's card (called green card, actually pink). To determine whether the NSA recorded the marriage, simply apply for a copy at the Dumaguete office of NSA, get it in minutes. But as I say, this is old information.