Iran having nuclear weapons is not a big deal, to be honest. Pakistan is probably a more dangerous country with nuclear weapons because it is intrinsically less stable than Iran, Pakistan is almost a fictitious country. Further, all of the terrorist activity in and around Pakistan means its nuclear weapons are in close proximity to elements that might be willing to use them in a terrorist attack.
North Korea is arguably more stable politically than Pakistan, as goofy as that may seem, they have had the same ruling dynasty since the 1940s, we’ll see how that goes going forward. While North Korea has/does ship weapons to terrorists North Korea is honestly so isolated that I don’t believe there is much risk of them ever sending their precious nuclear warheads overseas to some terrorist group.
But anyway, if crazy North Korea isn’t going to nuke people I can guarantee you that Iran won’t. Yes, we all know Iran is ran by Islamic fundamentalists, but I’ve seen no indication they genuinely would be happy to have their entire country wiped out by a nuclear exchange. If North Korea or Iran were to ever use nuclear weapons it would be essentially in response to a full scale invasion, and even then they would probably only launch them after trying to bluster/threaten the invading army out of their territory first. I think at that point, when the respective regimes saw their end was nigh, they’d potentially just say “fuck it” and launch, since they wouldn’t care to take the rest of their country with them at that point.
For that reason it really isn’t in the strategic interests of the United States to expend vast military resources to prevent Iran from developing nuclear weapons.
I will say if I’ve learned one thing from Afghanistan and Iraq, I do know if I was tasked with coming up for a military plan to end Iran’s weapons program it would take a very different form from the invasion of Iraq or Afghanistan. I can think of some ways we could do economically.
What first comes to mind is a full scale invasion, just like with Iraq I do not believe Iran’s armed forces would be able to protect the country very long. They would quickly be wiped out of the field. The actual goals of the invasion would be to destroy Iran’s conventional military, its command and control, and to destroy all of the nuclear facilities (unlike say, chemical weapons labs the nuclear facilities are all well known, albeit very hardened and dispersed so a single air strike wouldn’t end them, but with ground presence they could be destroyed.) After that, I would tactically retreat from Iranian territory.
At that point I would lock down absolute air superiority, and begin communicating with the President of Iran (whoever that might be.) I would tell the President of Iran that we would pay full reparations for any damaged infrastructure, this would be in direct monetary payments. Further, I would pledge payment of $50bn/year for 10 years that Iran’s government could use to do whatever it wished. From them I would only ask full and unrestricted access by nuclear inspections teams in perpetuity. If the President of Iran did not agree to this using my uncontested air superiority I would proceed to destroy every power plant in Iran, all the water treatment facilities in every major Iranian city, and would endeavor to destroy their major port facilities in the Persian Gulf and would essentially mine them so heavily as to make them unusable. Then I would simply monitor the situation and make sure they didn’t try anything crazy like try to restart their nuclear program (I am not sure they would be able to at that point) and respond as necessary. Since in that scenario I would not permit Iran to develop a significant military I would essentially have perpetual flyover capability. I suspect eventually the government would fall and be replaced by someone willing to negotiate a return to the 21st century for their country.