Nobody wants nuclear war-but if we got nuked, the terrorist nation(s) responsible WILL be flattened to oblivion. There will be no second chance for them at retaliation, they will cease to exist.
We are not going to flatten nations. I don't understand why people say things like this. It makes us sound like we have no control. The United States will have a measured response to whatever happens. Don't look for Iran to be sending nukes into the United States (or anywhere else for that matter.)
I am sure that Israel and the U.S. has a plan to deal with Iran. I would imagine North Korea would be more tricky. Hopefully China will take care of them.