In what way do you classify Iran as a third world country? They're wealthy, educated, enjoy a high standard of living and are capable of building nukes.
You forgot to add "...and they don't kiss US hinie", because that's the main reason why they make you nervous. They're not your boys. See, I believe Pakistan to be politically much more unstable than Iran. But you don't see americans freaking out because Pakistan has the bomb. Why do you think that is, Mycroft?
I suggest you spend some time here: http://www.cia.gov/cia/publications/factbook/geos/ir.html