I reasonably new to all this, I am looking at buying some points to get some frequent flyer seats with AA. Did a few searches, leaving Australia it seems most flights are link to Qantas, BA. Is it possible to book flights on Cathay, JAL, Qatar and other One World members? What is AA USDM?
Have you had a read of the article below?
Guide to buying AAdvantage miles for cheaper Business & First Class travel with oneworld partner airlines
You will have to ring up AA help line to check availability or use a BA account to search for availability on other partner airline flights.