Any order by Iran for Airbus aircraft will depend on granting of US export licenses. I’m not saying the USA will deny these, but still……
Er, I think that Airbuses are ITAR free, meaning the US has no say whatsoever. They're making A320s in China, and a while back there was talk of turning making an ITAR free MPA from an A320. A very large chunk of Airbuses are European through and through. The parts that come from, for example, Honeywell are unlikely to be contentious anyway.
The international sanctions that applied to Iran up until very recently were a different matter. Amongst other things that the UN sanctioned, the US used their banking might to stop financial institutions all over the world to stop doing business with Iran.
Companies do have to be quite careful - Toyota is having to explain why ISIL are driving around in shiny new Toyota pick-ups. They're not supposed to be able to get hold of them...
The only conceivable ITAR problem would be if they wanted GE engines. But then there's always RR and the CFM engines are part French anyway.
The US couldn't believe that Alenia built an ITAR free satellite and sold it to the Chinese. They kicked up one hell of a fuss over it, didn't get anywhere.
With the US not necessarily being the hotbed of R&D (of this sort) that it once was (a consequence of reduced defence spending), they're going to have to accept that other countries are perfectly capable of out-developing them in high tech stuff. Plus American companies cannot afford to be restricted by their own government's rules. So they develop outside of the US if they have to (AMD in Germany, Intel in Israel, IBM all over), even if the fundamental research was originally done in the US. The constitution's freedom of speech clause overrides ITAR.