OK, so, now you're saying that having the US bogged down in another country, not possessing nukes, is what has kept the US from invading Iran.
Yet, the US has not been in Iraq for a while now and while Iran still has no nukes, the US hasn't invaded. That also seems contradictory to what you originally posted. Further, the US seems to have had no qualms about being in Iraq and Afghanistan at the same time, so invading Iran, with its lagging nuke tech, would seem to be no problem. But, again, that hasn't happened.
You should at least be honest about why you want nukes: you want a big stick to wave around and feel like you have some power and get some respect in that part of the world. Not that that would win you any more friends amongst the nuclear powers, but at least its not some bullshit lie like "this would be the only thing preventing the US from invading."