The EU has already figured this out with the recently passed instant payments regulation [0]. As of 2024 are 5,304 banks in the EU [1], so the number of banks really isn’t an excuse. The US banking system lags the rest of world by a mile, because there is no will to force modernization.
FedNow is a technological solution for instant payments, not a regulation. It’s a voluntary system for the banks to join. Further, banks are not required to offer instant payment services to their customers. The analogous technological solution in the EU is TIPS [0], which has been operational since 2018.
The IPR is a regulation that requires banks to support instant payments and offer them to customers.