The key determining factor could be whether any American boots land on the ground or not. Once they do land, there is then no end to the op. I am assuming a simple Venezuelan-style kidnapping of their leader won't work here, or it would have happened already. Fwiw, Iran of course is substantially larger than both Afghanistan and Iraq, so the risk of a prolonged operation is longer.
The US totally botched Afghanistan, Libya and possibly Syria as well. I gueass another civil war is somehow better than rabid religious leaders who hate the US and Israel armed with nukes.
Ironically, this time, time would have been of the essence to save the protesters who died. Maybe the US noticed all their potential supporters were rapted and killed.
That was the public facing attempts to gather support. Internally within the administration, they started working on invasion plans within a few months of 9/11. These plans continued to iterate up to being more or less locked in and approved (by Bush) in Jan 2003.