The pan-Arabic nationalist movement wants one thing - to destroy the U.S. financially and they're willing to make incredible sacrifices to that end.
Can we AFFORD a long war - an occupation - of Iran?
Could we do it? Of course. We could easily dismantle Iran's conventional Forces. With about 200,000 Troops. However to occupy a country like Iran? Hell man don't even try with out 750,000 Plus Troops.
I don't think we need to do that anyways. I think we could use air strikes, and some special forces to Decapitate the Iranian government, and perhaps make some contacts in the Democrat Opposition groups in Iran, to work out how to help them take over the country.
Much like Libya.
Really though All I think we really should do, is determine if it is possible for us to Destroy or Seriously set back, their Nuclear program.
Iran is not a conventional Threat to us or it's Neighbors.
Oh sure they could invade Iraq, or Afghanistan yep. However US Air and Naval Forces excel at one thing. Decimating Conventional Military's in the Field. There really are not to many places in the world, where a country could move large numbers of troops, and tanks and trucks. That we could not easily destroy. Iran's Air force would not be any more effective than Iraq's and would likely not even try to fight us.
A lot of people seem to be under the false impression, that just because we struggle with Occupations, that we are some how weak now. Nothing has changed pertaining to our Abilities to Control air space, and Systematically Dismantle Anti-air systems, and Utterly Destroy Armies in the field.
We are still light years ahead of anyone else, when it comes to that.