There are two routes open depending on what you actually want to do. You can obtain a licence validation whereby you get a Restricted FAA Certificate based on your existing licence which is adequate for recreational purposes, or you can obtain the full FAA Certificate based upon taking the multichoice exam and a flight test. Both routes have been complicated post 9/11 due to TSA requirements and the need for foreign
licence validation before you go. Its no longer possible to walk into a FISDO and come out with a Temporary Certificate Airman whilst the main certificate arrives later through the post. Like air travel generally its become a pain in the arse.