If it DID become necessary to insert ground troops...we could do so on a limited basis and could do so effectively.
All that said, we would NEVER ATTEMPT an occupation of Iran. We'd just "break" it.
My concern is that airstrikes would just give Iran a “legitimate” excuse to just blatantly mobilize its military elements in response. We’re not dealing with the most submissive people here. If we’re too aggressive, I fear it could just make things worse.
I concur with Mariner. Iran is likely one of those rare situations that can be solved with airpower alone. Their air force is no match for us, so we would have air dominance early on day one, killing everything that flies and taking out the ground-based air defense stuff. Then we can destroy the nuke facilities. After that it depends on goals. One option would be to destroy just the Revolutionary Guard and whatever mullahs we can get and then see how the Iranian regular military handles things from there. The other option is to crush their entire military as well as the Guard, and a third is to just keep going until their infrastructure is so ruined that they literally have to choose between nationhood and having a nuke program.