If you can manage to meet the experience requirements for the FAA ATP you'll save yourself a bit of mucking around. The FAA CPL flight test ('checkride' in USA-speak) involves manoeuvers that aren't done for Oz licences eg turns around a point, chandelles, figure eights around ground points etc.
You would have to do two exams & two flight tests to get CPL & CIR equivalent privileges in a multi *or* a single. Then another checkride to add the remaining single or multi, respectively ie iwhich ever class you didn't get tested in initially. It doesn't matter which sequence you do the single or multi CPL checkrides, but make sure you do the IR in a multi so that you have IR privileges for both singles & multis. Obviously the multi-IR checkride must be done after the multi-CPL checkride.
If you meet the ATP requirements you will need to do only a single exam & single flight test to get ATP privileges (which includes CPL & IR privileges) in a single or a multi. Add a second ATP flight test to add multi or single privlieges, respectively, similarly to the CPL. Unlike the CPL or PPL, the FAA ATP has integral IR privileges. The flight test is pretty much an IR flight test with slightly tighter tolerances eg 1/4 scale deflection for LOC & GS.
You could do the CPL ATPL checkrides in an amphibian. That would give you both land & sea privileges at that licence level and for that class (single or multi) after a single test, instead of doing one test for land aircraft and a separate test for sea for the class.
Because you hold an ICAO professional licence you don't need to do any minimum flight training before the CPL or ATP checkride, nor do you need to get an FAA PPL issued on the back of your Oz licence to practice first. Find an examiner (FAA or FAA approved examiner) and do the test. Examiner is free if done with the FAA. Either way I'd *strongly* recommend you fly with an instructor first. The US rules & ways of doing things can be rather different to Oz!
No matter what licence(s) you do, you'll have to jump through the TSA insecurity crap first.
Last edited by Tinstaafl; 27th Apr 2010 at 01:44.