I wrote about Trump and Iran today:

With proxy forces across the region, Iran has cards to play, and the regime is inherently dangerous. At a time when it should be doing everything to curry favor with the Europeans, one of its diplomats was arrested a few weeks ago in Germany for plotting a terror attack on an Iranian opposition group in France.
But Iran lacks several advantages enjoyed by North Korea. It doesn’t have an overwhelming, powerful patron like China. It unites Israel and the Arab states, and none of our regional allies are pressuring us to negotiate with Tehran the way South Korea pushed us to talk with Pyongyang. Finally, Iran doesn’t yet have nuclear weapons.
This gives the administration leverage. The mullahs shouldn’t fear presidential tweets as much as the economic clampdown to come.