Going from Australia to the USA straight onto a 73 or 320 atm just isn't possible. I only know of 1 regional right now taking E3 pilots and from what the recruiter has said that's only for people who already have an FAA ATP licence.
There have been rumours over the last 3 years that Spirit, Frontier and Allegiant will take E3s but so far I only know of 1 person that has done this. Atlas has also taken E3 in the past but those people already had an FAA license and over 1000 hours USA part 121 time.
Even if USA cargo and LCCs do start taking E3s, I suspect they will pluck them from a US regional long before they take you with no FAA license.
I was at an Allegiant job fair pre covid and the recruiter said that they will take 1500 hour instructors straight from a flight school job before they sponsor a foreigner.
So the pilot pool will have to be very dry for some of the predictions above to come true.