But you are not sending money from US to Iran.
You are sending money from US to US, from Iran to Iran, and from btc address to btc address (A btc address has no geographical location of course).
Note that no fiat currency ever needs to leave either the US or Iran for this to work.
Important thread. This is how correspondent banking works, with the money center bank in the middle with offsetting correspondents in local jurisdictions. Knowing all the local bitcoin exchanges would allow anyone (almost anywhere) to receive and then sell bitcoin; however, the majority of exchangers are now registering and becoming AML compliant in their countries of origin, which entails identity verification of exchange clientele. This is still an evolving legal area and certain jurisdictions are evolving faster than others. In fact, some bitcoin exchangers are actively promoting regulation, thereby seeking to legitimize themselves (i.e., Intersango). I cover this in my post http://themonetaryfuture.blogspot.com/2011/11/air-guitars-and-bitcoin-regulation.html
Also, see this Reuters article, Bitcoin exchanges offer anti- money-laundering aid http://www.reuters.com/article/2011/06/15/financial-bitcoin-idUSN1510930920110615