Don't tell me the webinar left out the part where it would be prudent to check award availability. That would be an egregious oversight.
FWIW it is possible to use AA miles to travel between Australia and the USA and it can be very good value (at least far cheaper than buying a commercial premium class ticket). I have done it myself before and assisted a few others in obtaining such award flights.
The key thing to understand is that your ability to fly on AA miles (or any miles / frequent flyer programme, for that matter) depends on award availability, which is not the same as just having a seat available for sale. Given that the Trans-Pacific market is notoriously popular for award redemptions (and also a good yield market for the airlines that fly it), it is difficult at times to find Business or First class seats on relevant sectors. Sometimes you'll have to fly indirect; e.g. if you were proposing to fly from Melbourne to Los Angeles, you may need to consider the option of flying via Sydney or Brisbane. If your ultimate destination is New York, you may want to consider flying via Dallas Fort Worth rather than Los Angeles.
You should also be prepared to be as flexible as possible with dates. There's a good reason for the maxim, "You do not plan your premium award travel around your vacation; you plan your vacation around your premium award travel." If you are thinking of travelling during known peak periods, the difficulty in finding award seats will naturally increase, usually non-linearly.
I would think most of these would have been covered in the webinar or the relevant Knowledge Centre modules.
Good luck and good hunting!