Yeah we could give deeper into this question. Yes, the US has not adopted the technical solutions for quick (usually essentially instant) and free payments that Europe has.

And Europe isn't perfect either. E.g. in Sweden bank transfers are only quick and easy on weekdays. But then again nobody uses bank transfers because Swish is instant and 24/7, and all banks support it.

So yes, it's a technical problem that a transfer is not instant, but the "surprising delays" mentioned by previous commenters are not due to any of that.

Or do you have in mind technical solutions for improving AML/KYC handling that would reduce legit transfers getting delayed?

Sure, systems (legal and technical) can always be improved, but "surprising delay" is a problem from law, not technology. So bypassing it with technology just means (de facto) breaking the law.

What I meant is that many banks do not offer fast payments/transfers as a service, but they could do it if they wanted.

The most common complaint I hear is that bank transfers take a long time to settle as a default at a protocol level, not that law enforcement manually interferes with them.

The second most common complaint I hear is that sometimes the transfer is impossible.

For the first there are solutions, newer SEPA transfer can complete in seconds because fraud checking is done faster; this requires some kind of widespread cooperation between banks and governments. For the second complaint there are often no (legal) solutions.

Yeah this is what I meant about the US being a bit technically behind, but this is not the same as the "surprise" delays referred to.