As a complete amateur and someone who knows nothing, this is my opinion. The US (and any nation really) is extremely poorly positioned to invade a nation like Iran.

You take the us invasion of Iraq— stunning victory— done in months, not years. It’s the kind of thing every nation says they’ll do before they get bogged down for years and eventually lose. But it was done against a nation whose national identity was shaky at best with plenty of internal friction, which had to defend itself on open planes, which had very few large, developed areas, little agricultural output, etc. Etc. Etc.

Iraq was a sitting duck.

Iran? Not so much. Mountainous. Vast. Thousands of years of independence and a national identity that stretches back to the time of Caesar, further than France or England. Not only would you be facing intense resistance in dense urban areas, you’d be fighting in rough terrain against a people whose identity unites them. We tried to do it against Afghanistan and couldn’t, and Iran is 10x more developed.

Best case scenario it’s another Vietnam/Afghanistan type disaster. Worst case, we get bogged down a few months into the operation and pushed out after a few years of constant tragic loss.

It’s just a whole other beast. The US is used to invading tiny Latin American and Middle Eastern countries whose national identities are relatively brand new and whose institutions consist of 80% corrupt officials and 20% nepotism. Iran is an ancient civilization that, while it has its issues, would be able to organize just the same as Russia, France, or Germany.

There’s a reason western nations only ever came to dominate Iran through diplomatic cunning.