Why would it be seen as provocative and belligerent? Because that's the way the US government would see it, or would choose to see it. Be honest. How many times have you seen Cuba referred to in the US media as "America's backyard" and so forth?

Why would it be correct to see it as provocative? Because it would be obvious in advance that the US government would react in that way, and therefore the action would have to be seen as intended to be intended to provoke that reaction.

The fact that the hypothetical anti-missile missiles on Cuba would pose no kind of threat to the United Sates in real terms is beside the point.