I sometimes used to get an alarming amount of grief entering the US because I had quite a few Turkish stamps in my passport as we used to go there a lot on holiday. I hate to think what would happen with an Iranian stamp!
The US government is very concerned about people who use Turkey as an entry point to nearby conflict zones in Syria and Iraq. When I applied for the Global Entry program the only interview question they asked me was why I had visited Turkey.
I have an Iranian visa in my passport, so I had to get a US visa to go to the US. I didn't have to talk to anyone when entering — the electronic thingy scanned the visa, and that was it.
