I did mine years ago, before the idiotic TSA insecurity
came into effect however...
* Check your logbook against the FAR requirements for the ATP. Make sure you check the definitions for the required flight times eg cross country.
* Jump through the
stupid TSA crap. This means you'll need to go to a SEVIS approved school ie one that can take foreign students.
* As well as get CASA confirmation of your licence
* Do a Class 3 medical. Class 3 is for private ops & adequate for a flight test ('checkride' in USA language). You would need a Class 2 or Class 1 medical for charter or airline work, respectively.
* Pass the single, multi choice ATP theory exam. You can self study from a number of available publications. Gleim, ASA, Jeppessen & King publish stuff for the exam. The exam is
easy! I found the most difficult part was remembering vis. & alternate requirements in statute miles & fractions. And the variety of approach light systems!
* Do the checkride**. You don't need an instructor recommendation to sit the initial ATP flight test but if you fail you'll need to do remedial training & have a recommendation. I *strongly* recommend you do a bit of training before your 1st test. They do things differently here. Procedures & practices are based on US 'TERPS', not ICAO. Sort of similar but with traps...
**Like Oz, the US checkride involves application level questions about the licence/certificate. Make sure you know your stuff. Don't pass the questions, don't get to fly.
Buy (or download from the FAA) a Practical Test Standard (PTS). It gives chapter & verse about the requirements of the checkride.
Be aware that US licences are segregated by level, category & class.
Level -= ATP, Commercial & Private.
Category = fixed wing, rotary wing, glider, balloon.
Class (for fixed wing) = Single Engine Land (SEL), Single Engine Sea (SES), Multi Engine Land (MEL), & Multi Engine Sea (MES)
A flight test in one class of aircraft will only give a licence for that class of aircraft. You would have to do another test (at whatever licence level) to add another class. For example, you could do a commercial test in a multi engine land & an ATP test in a single engine sea and would be limited to commercial privileges in the MEL in spite of holding an ATP for a SES - and not be permitted to fly a SEL or MES.