The United States reacted to learning about Soviet missiles in the country of Cuba by putting a quarantine into place.
This quarantine was essentially a blockade around the island. The US Navy stopped any new ships from the Soviet Union from bringing in goods/resources into the country of Cuba.
After this quarantine, the US and Soviet Union negotiated a deal on how to settle this in order to prevent an all out nuclear war. In the end, the Soviet Union removed their missiles from Cuba under the inspection of the United Nations and the US agreed to remove their missiles from Turkey. The US also promised to never invade Cuba again.
