The only way that you can use AA miles to go from US to Australia via Asia is with the use of 2 awards . This will cost 37.5k/70k/110k (economy/business/1st) US-Asia2 plus 30k/40k/50k for Asia 2-Australia
Since this is 2 awards, there is no issue with stopovers
To use a 40k/80k/110k award for US to South Pacific , you need to go directly from North America to South Pacific without entering another region