An alternate history cliché when, for little reason whatsoever, a surviving Confederate States of America just expands and takes over Cuba and enough northern Mexican provinces to get to the Pacific, despite the lack of resources that make the Confederate States a bad candidate for Imperialist Adventures, and the lack of a political will for expansion. Not to mention that the pre-civil war drive for Expansionism was motivated by a desire to keep the balance between slave states and free states in Congress.
Oh, and that's not mentioning the whole issue that not much after the American Civil War (1868 to be exact) the Cubans started fighting a long and bloody war for independence, which IOTL ended in the Spanish American War of 1898, where emancipation was one of the stated goals, and equality was the ideal. A bunch of Slaveholders aren't exactly going to be able to win them over if the curent batch aren't too popular.