Process is very straight forward but time consuming. You do need TSA clearance, you do need a student visa, you need to get your Aus license verified by the FAA, this can take a couple of weeks. Then write the FAA ATP written, study for and do the oral, and do the flight training and get a sign off to do the flight test. Do not make the same mistake as many, the writtens might be easy compared to ICAO, beware of the oral and flight test. OR if you are doing a Type rating that will incorporate the oral and flight test.