Nobody is going to war against America for Tehran, Iran has no friends, no allies.
The Russians won't fight for them, neither will the Chinese, thus it becomes a rather one sided affair against Iran.
There won't be any land invasion, Iran is too big for that, none the less, they are easily bombed into submission
Iran's actual adversary is Israel, Iran can't afford to have their military decimated in the face of the IDF
America, NATO & Israel v. Iran : nolo contendere.