Short answer: Cuba was never formally owned or annexed by the United States, but it experienced de facto American control from 1898 to 1934.
U.S. defeats Spain; Spain cedes Cuba, Puerto Rico, Guam, Philippines. Cuba nominally independent but occupied by U.S. military.
Forced into Cuba's constitution, granting U.S.:
Platt Amendment abrogated under FDR's Good Neighbor Policy. Guantánamo lease remains. U.S. economic dominance continues.
Castro overthrows Batista; U.S. breaks relations (1961), imposes embargo (1962).
Unlike Puerto Rico, Guam, or the Philippines, Cuba was never a U.S. territory. It was a protectorate in all but name—sovereign on paper, constrained in practice.