Castro came into power, and that meant Cuba would be no longer an ally of USA. Castro, in 1959, overthrew the American-backed dictator Batista. Castro allowed Soviet army to enter the country which meant that Cuba was a new pro-Communist state.
To begin with, when the USA broke off relations with Cuba, there had been increasing suspicions between the Soviet and Castro. In 1961, President Kennedy supplied arms, equipment and transport for 1400 anti-Castro exiles to invade Cuba and overthrow him. The exile landed at the Bay of Pigs. However, they were defeated by 20000 well equipped with modern weapons. The invasion failed and came to be known as the ‘Bay of Pigs’.
The attempt of the invasion encouraged the spread of the communism. The Soviets flooded into Cuba. The soviets announced that it was supplying Cuba with arms. By next year, they had become the best equipped country in Latin America. Every main supply was supported by the Soviets like the petrol boats and tanks. The Americans watched with great anxiety. They were worried whether the Soviets would put nuclear missiles on Cuba and Kennedy made a speech warning the Soviets by saying ‘by whatever means might be necessary’.
Furthermore, with the growing tension between the USA and USSR, there was the October crisis in Cuba. The American used U-2, which was the hi-tech spying using equipment and the USA could confirm by the evidences taken by the U-2 that the Soviet built the nuclear missile sites in Cuba. Now it was Kennedy’s job to make its decision on what to do on Cuba.
To sum it up, it was a failure for the USA because it gave the USSR an opportunity to spread the communism instead of stopping them from being aggressive. In my opinion it might had contributed in leading to the Cuban nuclear missile arms race among the two powers.