[swat535]

How are you going to flatten Iran? A country twice the size of Texas with 90M people.

You would have to fire your entire nuclear arsenal and commit mass genocide.

Even then, you may not be able to destroy the missile cities, many of them were built to be nuclear resistant.

[genocidicbunny]

I'm not saying it's possible to accomplish that, just that directly harming the comfort of the American populace is a good way to unify large parts of said populace in wanting to destroy you. There's a non-zero chance of increasing America's appetite for war rather than reducing it with such actions.