A complete regime change would probably only come with a large scale invasion, bigger than Iraq's. A huge majority of Americans don't want that.
We take the Second Amendment for granted here in the US - but the lack of a similar thing in Iran is what will keep the civilian population under the regime's control - or else another 10k-30k+ massacre.
How would you feel if your city was being bombed by a hostile foreign nation, including a school full of kids? Magnanimous toward the attackers?