there is probably talk at high levels among the dem party, their allies, think tanks, and non-profits, that this shit is hurting them and super unpopular with the electorate. i literally could have told you this like a 10 years ago and saved them billions but whatever. it's the most obvious shit in the world.   the above reasons are why it won't happen. iran has to like, do something to actually warrant a war, and second what next? who takes over? more nation building? that just invites people in who want to take usa down a peg to wage war.  the neo-cons had a whole slightly overly ambitious plan to hem in iran and surround it to contain it.  but... (and this is the most important part) it's no longer needed because the sanctions have crippled iran anyways. they're a paper tiger.
Canada