Has something changed regarding the process? I remember doing mine about 1-1/2 to 2 years ago and all I did was go to the US embassy and they gave me an letter basically saying that my DL was a valid US licence and attached a copy and notarized it. I then took the letter, along with my passport, a number a copies of my photograph to JPJ, filled out a form and waited until it was approved (took about 5 weeks), upon which time I went back and picked up my license.
A friend of mine, who moved here recently, repeated the process today. He went to the embassy and had his and daughter's licences copied and verified, then went to JPJ and was sent away. They said he needed something else from the embassy besides the certification letter that I had. They also requested copies of his marriage certificate, wife's IC, daughter's work contract and a number of other things. A real freaking hassle to say the least. They weren't clear what the letter from the embassy was to say, and seeing how he was just there last week and picked up a letter I'm not sure that there is such 2nd letter.
I remember when I did mine other than the five week wait for the approval the process was actually pretty painless. Not a huge wait at JPJ to submit the application, almost no wait to pick up the license when it was done, no additional paperwork other than the passport. They even issued a 5 year license even they I had only a 2-year work permit at the time. But they hinted that the license once issued would expire in his case at the end of his 1-year spousal visa and he'd have to come back after it was renewed.