Can you carry enough fuel to do a non-stop flight from NYC to HKG or SIN or SYD? (You give SFO-SYD as an example, so NYC-HKG should be possible I suspect.)
Oh, I guess the issue is the boom. What about flying subsonic over populated Canada, and then (slightly shifting the conventional NYC-HKG route) head over Hudson Bay to accelerate to supersonic velocity?
The return route is often done over the Pacific (because of prevailing wind patterns), so there would not necessarily be a need to sonic boom over southeast China.
The return route is often done over the Pacific (because of prevailing wind patterns), so there would not necessarily be a need to sonic boom over southeast China.