There would be lucky to be 5000-7000 current ATPL holders in Aus 2-3000 of those probably work at QF the other 2000 at VA and other random carriers. I don’t think the few hundred heading the US will make much difference. AA alone has well over 13000 pilots with the majority at retirement age in the next 5-7 years.
My numbers may be way off just spit balling, but the US job market is massive compared to down under. 10000 E3/year have been available since 1995. They rarely issue more than about 3-4000, historically not many of those would have been pilots.