Maybe instead the US should honor their commitments which would include the Iran Nuclear deal that was scrapped for no reason 5 years ago.
I'm not going to speculate how good it would to attempt regime change right now but there was a very good opportunity for it when Iran had unrest and they came to a genius idea to murder around 15000 arrested people.
The best opportunity would have been of course when US had sizable military formations on both sides of Iran border. On top of it it would have very likely limited large number of civilian causalities in Iraq due to reduced activity of Iran backed terrorist cells.