Had little to do with safety but more with the fact that no US manufacturer had been able to come up with something similar.
**************************************************
More narrow minded garbage.
Boeing were developing a much more awesome SST, the 2707
at this time. Supersonic craft were no major achievement during this era. The Soviets (at that time) were orbiting Zond spacecraft around the moon and the US were landing Apollos on the moon.
Hypersonic X craft had come a long way even before the Concorde flew, so other nation's technology was far ahead of the 'so beloved' Concorde's technology.