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.
Hyperbole is a useful way of letting off emotional steam- it's much better than going out and starting a physical fight in order to vent. I think most people accept that it's mostly hyperbole.