Hrmm, I have to shoot a hole in that one Savak. Whilst you are right in that Iran would be the most potent military threat to the United States to date, they are by no means any match for the US or especially a more likely coalition force that would be involved were there to be an invasion.
Iran is not a potential threat to the united states to date. It is only a threat in sense of American interests are being threatened with the growing power of Iran in the region. lets not forgets every country west of the persian gulf is an American backed dictator.
Anyway, an invasion of Iran is unlikely, the only advantage of that for the US would be a regime change and some control of the oil there. It would be way to costly and the US is preoccupied with Afghanistan and Pakistan at the moment. If there is to be a military solution it would have to be a surgical strike or a single blitzkrieg like attack on the nuclear facilities.
Not that I'm a military tactician though
An invasion Will not happen and neither a military strike on nuclear reactors either. Neither would Israel do anything without big brothers permission.
I think Nuclear missiles are the only danger for Iran. Otherwise they can give as well as they get but will be defeated in the long run. All American bases are within range. America cannot keep their airfields out the Iranian reach.
The best thing for Iran to do would be to sign a mutual defense pact with Syria, so if one gets attacked the both go to war with the attacker. If Iran is attacked there is no doubt Syria is next so they may as well pre-empt it.
That way if the US attacked they would no doubt beat Iran but the consequences for American troops in Iraq & Afghanistan would be carnage, non-stop. And with western society valuing human life to such a high degree, sooner or later something back home will cause a withdrawal. there is only a number of troop an aggressor will sacrifice.