We have satellites tracking EVERY missile launch in the world.
An Iranian nuke would not be large enough to cover the entire US. It would need to be bigger and higher for the cone to cover the continent.
Iran would cease to exist.
They are bad guys. But they are not stupid.
“We have satellites tracking EVERY missile launch in the world.”
But how do you trace the origin - with 100% reliability - of a missile launched from a barge located 100 miles off of your coastline, when the origin of the barge itself cannot be tracked, and the barge itself is sunk immediately after launch?
You said it yourself: “They are bad guys. But they are not stupid.” If they can build nukes and rockets, they are smart enough to hide the origin of a weapon, or to leave just enough clues to pin it on someone else. So, IMHO, there is NO guarantee that the nation launching such an attack upon us would be caught (and incinerated 30 minutes later). Frankly, were I leading Iran, I’d try to frame the (Godless) Chinese. No one much likes them, and they present a threat to both the US and Russia; for the Iranians, they get to both attack and devastate the Great Satan (the US), and then have the Great Satan nuke the crap out of a bunch of Godless Communist infidels. So long as they don’t get caught, they win all around. They would just have to fool us for a little while - until whomever was POTUS felt enough confidence (or pressure) to launch and hit back at SOMEONE.