Cuba was ruled by a pro- American ruler but soon he was defeated by guerrilla forces of Fidel Castro who become the new ruler of Cuba. Because of US support to the last tyrannical regime he was anti imperialist and joined hands with communist Soviet.
Communist ally on the sea shores of Miami was unacceptable to US administration who tried to kill Fidel Castro and failed, for 638 times!
CIA hired his maid to feed him poisonous pills, hired a agent to deliver contaminated cigar, thought to gift him a dress with bacteria that will kill him but all plans failed and the Cuban Revolutionary leaders survived even after 10 US presidents were changed.