US based airlines love a hub, but Aussies not so much. Clearing immigration in DFW is much quicker than in LAX, helped by fact the SYD-DFW flight lands at a unique time, so its only people off that flight using the e-gates, and the dual luggage carousels split by class speeds things up too. But Id always be prepared to pay a reasonable premium to fly direct on QF, than have to switch to a AA domestic connection.
Not sure about the demand on this one, unless you are thinking people wanting to ski in BC would fly to SEA then bus/train/drive up to BC in snow season? I quire like Seattle, however its not somewhere i visit nearly as regularly as NYC, ORD or SFO. I'm interested if BNE-ORD will ever get to start.
Id be more like to fly SYD-BNE-ORD to avid AA metal, than SYD-DFW/LAX-ORD (on QF=AA).