It's not exactly a fact. In my view Concorde was killed by a 'perfect storm': changing market conditions, 9/11, that terrible crash in Paris.
Together those three were what caused the towel to be thrown into the ring. Every time I visit Paris and I see it impaled on its stand it reminds me of a butterfly or something trying to escape. Such a sad image.
In many ways, the Concorde was "dead" well before 9/11 or the Paris crash. Yes, those killed it for good, but costs, sonic booms (US landings were initially banned, then limited to JFK and Dulles), and politics killed the concept shortly after it was launched.
Yeah, the lack of supersonic overfly on most countries (not just the USA) was one of the main factors against Concorde (despite the fact that in many cases the decibel levels were lower than cotemporaneous aircraft).
It's no coincidence it's main routes (London->JFK, Paris ->JFK) are 90% over the Ocean.
If you actually managed to get long distance hypersonic routes (such as London->Sydney, or even London->Beijing, London->Tokyo, etc.) at a significant time reduction, I can see it working.
Together those three were what caused the towel to be thrown into the ring. Every time I visit Paris and I see it impaled on its stand it reminds me of a butterfly or something trying to escape. Such a sad image.