Consular Presence
The United States maintains no official presence in St. Kitts and Nevis. A U.S. consular agent residing in nearby Antigua, however, assists U.S. citizens in St. Kitts and Nevis. U.S. EMBASSY TO BARBADOS, ANTIGUA AND BARBUDA, DOMINICA, GRENADA, SAINT KITTS AND NEVIS, SAINT LUCIA, AND SAINT VINCENT AND THE GRENADINES-https://bb.usembassy.gov/contact/#emergencies
There is always a US Consular agent in countries where cruise ships visit.