Distance wise, SYD to TPA (with stops in HKG and LAX) is about 14000 miles each way. Yes, you can include domestic USA flights on AA for free in an award.

http://www.gcmap.com/dist?P=syd-hkg-lax-tpa

According to the Asia Miles award chart, a plain vanilla return biz class award ticket will set you back 175k miles (per ticket) plus taxes and fuel surcharges

https://www.asiamiles.com/am/en/redeem/charts

A similar award using AA miles would require two tickets, as AA does not permit USA-Australia awards via Hong Kong. For a USA-HKG and HKG-SYD ticket, the total cost would be 180k AA miles (but AA won't charge you any fuel surcharges for travel on CX)

https://www.aa.com/i18n/disclaimers/...rtnerChart.jsp

I didn't price an award using BA Avios for your preferred routing, but it will probably be similar in mileage cost since you are dealing with a minimum of three segments each way (BA's award chart is distance based PER segment)

Note that the above mileage costs would be lower if you were happy to fly a more direct (NO CX) routing across the Pacific, i.e., SYD-LAX-TPA/SJU will cost less in terms of miles on AA, BA and Asia Miles. For example, only 145k Asia Miles or 125k AA miles.

The best deal for your routing would be to use the US Airways award chart but US miles are no longer so easy or cheap to acquire (from Australia). They allow transits in HK and the total price would only be 110k miles in business. US Airways has the least flexibility though in terms of making date changes (you can't once travel starts).

http://www.usairways.com/en-US/Resou...wardtravel.pdf