There's no mention of her telling the clerk that she was a U.S. citizen. She told him "I'm from Iran". What's he supposed to do in that case? Can't blame him for not taking the risk. That's a serious federal law (and it's not unheard of for the feds to run sting operations, when it comes down to that).
The other guy was definitely trying to buy the device for an Iranian citizen.
The other guy was definitely trying to buy the device for an Iranian citizen.