Bottom line:
America was and is fully capable of building an SST. We had a mach 3 bomber flying in 1964.
Concorde was a waste of money and owns the worst saftey record of any major aircraft flown today by far. Crashes per departure the worst of any airliner by a VERY large margin
Britain and France are not making any more Concordes because it's a waste of money, pure and simple...... unless they forgot how to make them.