I don’t think a cruise missile is a major threat. I think a EMP attack with crude scud missiles from a launcher in a cargo ship is far worse. Read the novel “One Second After” if you don’t believe me. I’d rather have a nuke land on my head than to go through that scenario.
The Iranian’s have the missiles, launchers, and have been seen off their coastline training for this type of attack. All they need are the warheads.
I do know about a potential EMP attack. And that should be a good reason for Iran not having any nuclear weapons.
But, the fact of the matter, there are several other sources for this happening, if they decide they have good enough reason and they are willing to take the blowback. There’s China and Russia. Either one of them can EASILY do that without any problem at all. They each may decide that they want a “new world order” in which they will come out on top, out of the ashes of everything afterwards.
And then, there are the terrorists, who can easily disguise the material and out it into place offshore, way off in International waters. Terrorists have enough money and the wherewithal to do that sort of thing.
It can be done if anyone puts their mind to it.