You reference a lot of what ifs, maybes, might be, could be, and could possible be speculations, ignoring five things.
(1) we faced “possible” immanent annihilation from the Soviets, who vowed to bury us, and who had capabilities many times over what the Iranians have, or even could have; yet we contained the threat through a combination of all the different and various means we had available;
(2)we should not be concerned about the Wahabi and the Theocrats in Iran “blowing each other up” - it’s not our problem and we have no stake in backing either one; neither one are our true friends;
(3)if other states in the Middle East, like Egypt and Turkey behave as if they too must acquire nuclear weapons capabilities, it will be not because we have become their next threat - and therefor their arms will not be aimed at us - it will be because they want to behave as if Iran or the Saudis so armed are a threat to them - oh, gee, that is not likely in any sense, so “proliferation” will not advance by that means;
(4)we have become experts at tracking the nuclear programs of other countries, like Iran and North Korea, and there is not much they do that escapes us; suggesting we do have the means to identify and interdict weapons technology transfers and we have the ability to vastly increase those abilities as well, should we need to; and lastly
(5)just what are we developing and building anti-missile defenses for in the first place - just for show, or because we believe they can work - yes, we believe they can work.
We never made a first strike on either the Soviets or North Korea, during a whole host of moments when either one was a much more serious threat than Iran is or will be - to us; though we had the ability to do so and “get away with it” many times. Why? The strategic threat was real but the moment that is needed - immanent threat - never arrived. We never had to “pull the trigger” and WE do not need to with Iran AT THIS MOMENT. That is not to say that Iran won’t continue to move the clock from “potential” to “immanent” - such as directly attacking Israel - and THAT would change our need to change our response as well.
And, as I said, Israel and its security context is a whole other matter. The Theocrats in Iran have vowed to wipe Israel off the map and their arms programs are directed at that intent as well as to become of the king of the hill in Islam.
If anyone is directly and immanently threatened by the Iranian nuclear program, it is Israel, and not the U.S. That might give Israel some legitimacy for a “preventive” measure against Iran (I believe it does), but not the U.S. - at this point. In that regard I am for a U.S. position that is NOT intent on preventing such action by Israel, should Israel determine it must take it FOR ITS OWN SELF DEFENSE. That context, could soon be “immanent” for Israel, and help justify such a measure, by Israel.
We are far from that being the case as it concerns independent U.S. action - at this time.
We came close to war with the Soviets on numerous occasions, the most famous of which was the Cuban Missile Crisis. Already, Iran is staging missiles in Venezuela. But the Soviets were rational actors. Can the same be said for the radical Twelvers who want the Muslim world to be purified with fire and who chant "Death to America"? But even largely rational states make mistakes. If Iran gets nuclear weapons, the per-existing nuclear programs of Egypt and Saudi Arabia will hasten. When a nuke is used by a terrorist group using a container ship or modified jetliner, who is to be held accountable. And even if we would trace the nuke, might it still not be rational for an Iranian leader to doubt the resolve of an American president in killing Iranian civilians in the millions to respond to an attack by Lebanese Hizbullah? Under those circumstances, would an attack by Iran by proxy be less rational than say the Japanese attack on Pearl Harbor?
(2)we should not be concerned about the Wahabi and the Theocrats in Iran “blowing each other up” - it’s not our problem and we have no stake in backing either one; neither one are our true friends;
OIL. Notice what flows out of the Persian Gulf. And see above.
(3)if other states in the Middle East, like Egypt and Turkey behave as if they too must acquire nuclear weapons capabilities, it will be not because we have become their next threat - and therefor their arms will not be aimed at us - it will be because they want to behave as if Iran or the Saudis so armed are a threat to them - oh, gee, that is not likely in any sense, so “proliferation” will not advance by that means;
And when an Al Qaeda like group takes over Saudi Arabia from the corrupt fundamentalists, using the same excuse that the Saudi clan did to overthrow the Hashemites? When instability allows a faction of a government to hand nukes over to one of 2 dozen terrorist groups, what then?
(4)we have become experts at tracking the nuclear programs of other countries, like Iran and North Korea, and there is not much they do that escapes us; suggesting we do have the means to identify and interdict weapons technology transfers and we have the ability to vastly increase those abilities as well, should we need to; and lastly
I'm not talking technology. I'm talking about giving a proxy a nuclear device or radioactive material for a dirty bomb.
(5)just what are we developing and building anti-missile defenses for in the first place - just for show, or because we believe they can work - yes, we believe they can work.
We should have these. But what would stop a cargo ship with a hidden nuke, or even a third party cargo ship with a container hiding a nuke? What about a modified old passenger jet carrying a nuke, that has a hacked ID code?