"All Iran has to do is hard tip all the missiles it got, and point them all at Jerusalem.
Problem solved.
Remember there is JUST ONE Jewish country in the world Israel and it is SMALL !"
I don't think that you'll find America held hostage from its range of options for fear of retaliation against Israel.
It will take a pre-emptive nuclear attack on Israel, and in a number of locations to destroy the state. Anything less like a chemical strike would assure retaliation without assuring Israel's destruction.
Judaism, of course, would survive in a number of other locations around the world, including America.
Likely gone forever, though, would be a good portion of antiquity and its treasures. Fair enough in that the same might be the case for Iran and many of its treasures from the past although I don't believe that anybody is discussing a western pre-emptive nuclear strike on Iran.
What would also be lost forever, though, is a Palestinian homeland. It would be radioactive dust...along with a lot of Palestinians, likely. Many Palestinians in the West Bank would be incinerated in those strikes. Maybe most depending on Iranian accuracy.
Certainly, though, very few living there of any religion will come through such a calamity unscathed.
In fact, the downwind drift calculus would be outright scary for any part of Lebanon, Syria, Jordan, and Egypt.
Such an event would cause a chain reaction likely to reshape the world as we've known it forever.