On more than 30 occasions, the United Nations Assembly has discussed the blockade against Cuba, which costs the island 5 billion dollars annually, according to some estimates. Every year the resolution is proposed and the whole world, through the vote of the absolute majority of the member countries of the United Nations General Assembly, has condemned the imperialist attitude of the United States towards Cuba.
edit: result of the vote: https://mastodon.nzoss.nz/system/cache/media_attachments/files/113/398/372/180/881/996/original/82c4d1f509e933fa.jpg
You are correct but the question was … why should a country prevent another country from being able to freely trade with every other country.
Every country has trade relations with everyone else. When you form pacts with other people you have to agree on terms together.