An atomic bomb costs about $65,000,000. Iran has 8 major cities. So that's quite a bit of money.
But you should also count on Russia, China, North Korea and perhaps Iran itself to send a few back, so that will reduce the price again.
I live 2200 miles from the Sahara, but the sky here this week turned completely red due to Saharan sand and the cars had a fine layer of sand on them.

I think atomic bombs on Iran and Israel will kick up quite a bit of dust.
Iran out of existence actually means that you will be breathing in Iran and Israel for the coming months.
You can then be sure that in the next conflict that America wants to organize, the Brics countries will push the buttons at the first senile tremor that Biden makes.
So whether it is a smart move? I don't think so, but it would be spectacular.
Just think of the beautiful sunsets you will get.
But the fact is, if you think it, then it's out there in the collective field. That means also that people who can push the buttons are considering it.
I propose that we do the same thing with war as we did with wolves.
https://i.imgur.com/Iko03mL.mp4