Wasn't Cuba a U.S. territory for a while?
Following the Spanish-American war in 1898, the US occupied the country of Cuba until the US turned over control in 1902. In 1903, the Cuban-American treaty set up the framework for relations between the two countries, including the ceding of Guantanamo Bay to the US as a military base to protect the island nation.
Just as throughout the history of the US, we turn over nations we occupy following the end of a war. Just think, if we haven't, the US would also include nations such as the Philippines (I could actually use my Tagalog more) and Germany.