Interesting side notes from some quick Wikipedia searches: the Age of Consent in the Philippines is 12, the lowest in Asia... but for prostitution (as I'm sure was the case here), it is 18.
(Other than those nations which require marriage before sex, the 1/3 of the US that is 17 or 18 is the highest in the world. 2/3 of the US has an Age of Consent of 16. Most of Europe is 14-16. Most of South America is 14. Few of these are solid numbers, though, as many of these countries and individual states/provinces carve out tons of exceptions, restrictions, etc. Some nations, like Bolivia, set it at puberty.)
The United States imposes its own age of consent standards on Americans traveling in foreign countries. This is separate from whatever standards may be imposed by those countries.
from http://en.wikipedia.org/wiki/Child_sex_tourism:
Tourists from the United States Under the PROTECT Act of April 2003, it is a federal crime, prosecutable in the United States, for a U.S. citizen or permanent resident alien, to engage in illicit sexual conduct in a foreign country with a person under the age of 18, whether or not the U.S. citizen or lawful permanent resident alien intended to engage in such illicit sexual conduct prior to going abroad. For purposes of the PROTECT Act, illicit sexual conduct includes any commercial sex act in a foreign country with a person under the age of 18. The law defines a commercial sex act as any sex act, on account of which anything of value is given to or received by a person under the age of 18.[45] Before congressional passage of the Protect Act of 2003, prosecutors had to prove that sex tourists went abroad with the intent of molesting children—something almost impossible to demonstrate. The Protect Act shifted the burden, making predators liable for the act itself. Penalties were doubled from 15 years in prison to 30.[6]