A tough long history of discord has severed the relationship between Cuba and the United States. Cuba was under Spanish rule until the Spanish-American War (1898). Under the Treaty of Paris, Cuba became a U.S. protectorate and America gained a position of economic and political dominance over the island.
But the relation had steadily declined since Castro seized power in early 1959 and leaned towards the Soviet Union by signing a trade treaty and establishing formal diplomatic relations. By the end of 1960, President Eisenhower cut Cuba's Sugar Quota and refused to export crude oil. Cuba nationalized the American-owned oil refineries without compensation and relied on Russian crude oil. America's retaliation included the Bay of Pigs invasion (1961) by CIA trained Cuban exiles and over eight attempted plots to eliminate Castro, etc. Tension between the two nations reached its peak in 1962 after the Soviet Union constructed intermediate-range missile sites in Cuba, which led to the Cuban Missile Crisis. The U.S. embargo against Cuba continued in varying forms even after the collapse of the Soviet Union in 1991. Afterward there were several attempts to thaw the relationship, but it was on and off depending on each US administration's foreign policy.  Obama shook hands with Raul Castro at a memorial service in South Africa following the 2013 death of Nelson Mandela. "Mandela showed us the power of action," Obama said in his speech, "of taking risks on behalf of our ideals." Then relations between two nations were formally re-established with the opening of each nation's embassy in Washing and Havana. But, the issue remains on how to resume economic relations between the U.S. and Cuba and to implement human rights.