Pinoy Pilot, to convert to US ATP, you need to pass the FAA written exam which covers 7 subjects, a flight test and an oral exam. The written is piss easy, but don't take the oral test lightly. There are schools that do reviews in Florida for the written exam. You can do it in one day. The flight test might be interesting though if you haven't done any flying in the states, so I would do 10 hours in a light twin just to familiarize yourself if you decide to do it.
The oral will be based on technical questions about the aircraft you fly but it's a killer.
Goodluck to all pinoy pilots, its time PAL realizes your worth.
DeltaSix