[rolling_stone]

Well according to the US State Department they can’t say for sure.

[kabar]

This is State Department policy based on existing US law, which would govern the status of John McCain:

Birth Abroad to Two U.S. Citizen Parents in Wedlock: A child born abroad to two U.S. citizen parents acquires U.S. citizenship at birth under section 301(c) of the Immigration and Nationality Act (INA). One of the parents MUST have resided in the U.S. prior to the child's birth. No specific period of time for such prior residence is required.