The USA had previously accused the Soviet Union of trying to build an empire in Eastern Europe, but had gone and done a similar thing, sending an armed invasion in attempt to restore control in an independent country) - embarrassing for the USA.
The Soviet Union were quick to point out how the people of Cuba were happy under the leadership of pro-communist Castro
Khrushchev said this was a clear example of the popularity of communism.
The incident led to stronger relations between the Soviet Union.
Castro asked Khrushchev for support defending Cuba against further attack from the USA
September 1961: Khrushchev announced he would provide arms to Cuba
This worried President Kennedy as Cuba would have modern military equipment and training from Soviet officials.
If Soviets decided to place nuclear weapons in Cuba, the USA would be even more at risk.
Kennedy warned Khrushchev he could not allow him to use Cuba as a base to threaten the USA - Khrushchev assured him this was not his intention (however this was later proved false)