OK, let's say for sake of argument that Iran was months away from building a functional nuclear weapon. Do you really believe that they would use this to stage an attack against the US, knowing that A. they would almost certainly be annihilated and B. that with a very meager nuclear arsenal, what few weapons they have would be intercepted/destroyed by US defenses regardless?
Weak nations don't attack powerful ones. Weak nations that do develop nukes or try to do so as a deterrent against being attacked. I'm not saying that a potentially nuclear-armed Iran is a great thing. However, the idea that it would be a mortal, existential threat to the US is absurd. China has many times the nukes that Iran could ever dream of, when's the last time China attacked the US?
If you think there’s a guarantee that other countries will not use their weapons against us then you are living in a dream world and have absolutely zero understanding of history. You do know that Japan and Germany were pretty thoroughly demolished in World War II which they started.
You also should know that the leadership in Iran is not rational that it is a group of religious fanatics.
The Chinese don’t believe in jihad and don’t think that becoming martyrs would be a great blessing. That’s why nuclear deterrence works with them, but not with radical Islamists like the Iranian theocrats.