Nuclear missiles in Cuba?

[Anomalocaris]

What the US has the right to do and what the US can do are two very different kettles of fish (not very different from any other great power).

Boru

The OP asked how the US should act not how they can act. The US should respect the right of a sovereign nation to enter into alliances even if they are not advantageous to the US. The fact could act like Russia and throw a hissy fit doesn't mean they should.

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If a country only does what everyone would agree it has the right to do, then the chances are it won’t be able to exercise its right to exist, even if everyone agree it has that right, for very much longer.

There is a difference between defending your country from imminent threat to its existence and flying into a hissy fit because one of your neighbors allied with a country you don't like to defend itself from you.

There is no fundamental adjudicatable difference.   You are living in a legalistic fantasy world, not a real one.