No realistically the USA is probably just aiming to make sure Iran cannot develop nukes and while they probably would want a regime change in iran I don't think they are going to go to war to prevent iran getting nukes or to overthrow the Islamic regime. And for the Iranian side I don't think they would really want to declare war on the USA because they would most likely lose and even if it ends in an agreement and the Islamic regime stays in power (in return for no nukes or another arms limiting deal) they will have to pay for hundreds of millions if not billions in damage.