They are absolutely nothing without a nuke.
With a single Nuke they can destroy a lot of American lives and whether or not we would retaliate with nukes is a question that would have to be asked.
A nuke or dirty bomb brought into an American city would be a disaster. If he doesn't have them, then we at least have the security of knowing that he can't use them against us.
Immie
But the likely future consequences of being so hostile towards them now is a larger conflict in which they ultimately will obtain nuclear weapons, and because of our history with them they will be even more likely to use them than before.
Iran will not willingly cease production of nuclear weapons. That means our only options are force. Sanctions and military action will only brew disconent and hatred towards the US. Maybe it will encourage Iranian youth to join terrorist groups, and then attack the US. Maybe these groups will obtain nuclear weapons, and create an even worse situation.
Iranian will be no more of a threat with nuclear power than it is without nuclear power. The only reason it is a threat at all is because we keep trying to tell them what to do. It all started in the 1950s when the CIA initiated a coup that overthrew their democratically elected leader and installed the shah as leader. Ever since, Iran has had hostile views of the US. Doing more of the same will only make matters worse, and cause another generation to become infused with hatred toward us.