Pretty sure Saudi Arabia where some of the people to help finance the 911 attackers, not Iran.
Not that Iran hasnt sponsored other terrorist groups, just pretty sure they had little if any involvement in 911.

A few things first Iran can best be described as a Theofascist State, as in a Theocratic Fascist State, it is more a sub type of Facism rather than its own specific thing.

Also Iran would likely not leave the USA alone if the left, because of the history between the two, and Iran's pride, the would still likely work to undernind the USA. And I tell you this as someone with Family from there.

Also just gonna be brutally honest here, if those in the Iran government had the power of the USA they would do stuff far worse than the USA, not saying this to excuse everything the USA has done, but just as a reminder the USA has some restraint with its power.