If you're just looking for an ATP-CTP course and doing it from your own pocket, Delta has one in KATL. I have no idea what it's like...and even less idea why an outfit like Delta would bother with stuff like this (I have a theory):
https://news.delta.com/new-pilot-cer...-through-delta
https://atpctp.delta.com/content/atp...n_US/datc.html
Sounds like you'd be career-destination airline bait here. When you get your FAA ATP, start firing off the applications to
EVERY airline you'd consider working for.
If you could stand the financial slap in the face, you could go to one of the US regionals taking your fellow Aussies and let them get you the FAA ticket at no cost to you. You wouldn't have to bother with the E3 visa...and neither would the regional. No loyalty to the regional is expected. It's a new world here these days.