Historically, in EU the private industry chose not to solve the problem because (just like in USA) the problem is profitable for them. Sometimes people need fast payments and you can charge them lots of money for that; if everyone's basic payments are fast and cheap, then you lose that revenue.
The point of change in EU was legally mandated changes (PSD) which (after a transition period, something like 2 years maybe?) essentially required banks to deliver payments within a certain time or compensate the payer for any losses/costs caused by the delay, at which point suddenly the private industry managed to quickly solve all the technical and organizational problems that were impossible before.
I think it's a bit odd we rely on governments to print and issue currency (estimates that only 8% of currency is physical), yet are very hands off about the digital side of things.
I think a few years ago there was a summit of US bankers to talk about creating a faster alternative to ACH. They decided not to (presumably because they didn't see any benefit to themselves).
I do keep hearing about "Same Day ACH" which was rolled out and phases and phase 3 was supposed to be done on March 16, 2018.
The point of change in EU was legally mandated changes (PSD) which (after a transition period, something like 2 years maybe?) essentially required banks to deliver payments within a certain time or compensate the payer for any losses/costs caused by the delay, at which point suddenly the private industry managed to quickly solve all the technical and organizational problems that were impossible before.