I'd agree with your characterization for "most", but the fact that something like the G650 series exists (~20 passengers, Mach 0.95, 10k+ km range) and sells implies that long range, high speed is also a viable niche.
That, plus the Global Express, BBJ, and others exist (and Falcon 10X is coming next year).
Those are also very usable within the US plus on inter-continental trips. If a supersonic-capable jet can only operate subsonic over the US, a lot of the utility drops off (and the compromises required to permit it would become annoying).
