American citizen[s] or national[s] may be subject to prosecution Under 18 U.S.C. §2423(c) Even if the person did not have the intent to engage in sex with a minor at the time he or she left the United States, such intent at the time of travel is not necessary. For example, an American citizen or national who travels to a foreign country without any such intent, but who engages in a commercial sex act with a person under 18 at some point during his stay in that foreign country, may be subject to prosecution
Section 2423(c) prohibits traveling in foreign commerce and engaging in any illicit sexual conduct. Section 2423(c) includes attempt and conspiracy, see 18 § 2423(e), and has a statutory maximum penalty of 30 years in prison.