The next escalation would mean probably flattening tehran entirely, and to me the easy option would be a nuke (remember how I bang on about Putin saying "one probably won't start ww3"?).
In reality the US could maybe do something economically, but I don't see that being any more effective than the last 40-odd years of sanctions. So what then?
I mean you fire a nuke and it's a no-holds bar rush for every super-power in waiting to take the power spot.