Hold on...is there even any oil in Iran?
Can't tell if serious or not, but Iran has an estimated fourth largest supply of oil, and second largest supply of natural gas. If you combine these, it's the most abundant source of hydrocarbons in the world. The US's issue with Iran is over theater dominance (the real reason we don't want them to have a nuke) and privileged access to energy resources (which we're competing with China for.)
Partly serious
What do you mean about the dominance? Does the US think it's actually got weapons? so it's honest to god and everything that ever was anything not just about control of the oil supply?
The US and most of the rest of the world think that Iran is an unstable country in an unstable region and that it would be a bad idea for all the countries in that region to have nuclear weapons to threaten each other with. Its a fair point. I don't think Iran can be stopped because it has a history of being pushed around by the US and the UK and it sees nukes as the only way to guarantee its sovereignty. But if and when they do get the nukes, a lot of other crackpot regimes will be after them too and that is a bad thing.
translation: "unstable region" == "region not under our control".
If the US/west hadn't been fucking about with the region for such a long time, this would probably be one of the most prosperous and stable regions of the world, maybe even a working example of democracy the western nations could use as a model to clean up their shit.