Russia's suitcase nukes have shown that a nuke does not need to be big, or overly heavy. Getting one of Mexico's knowledgeable coyotes to carry it across the border in an old Volkswagen and then set it off in, say, Dallas, would suffice. Iran doesn't even have to make the nuke on its soil; it can outsource the job to somebody else willing to be vaporized for Allah.
"Iran doesn't even have to make the nuke on its soil; it can outsource the job to somebody else willing to be vaporized for Allah."
You mean, once Iran starts manufacturing nukes, they could export some key components and have someone in another country actually build it, maybe with some local content added?