Authors:

If you look at US internal documents, they explain very clearly what the threat of Cuba was. So, back in the early 1960s the State Department described the threat of Cuba as Castro's successful defiance of US policy, going back to the Monroe Doctrine. The Monroe Doctrine established the US claim to dominate the Western hemisphere and Castro was successfully defying that. That's not tolerable. It is like somebody saying "let's have democracy in Greece," and we just can't tolerate that so we have to destroy the threat at its roots.

Source: pennpoliticalreview.org
If you look at US internal documents, they explain very clearly what the threat of Cuba was. So, back in the early 1960s the State Department described the threat of Cuba as Castro's successful defiance of US policy,