Australia has fewer still, with the big 5 almost entirely dominant, yet we have instant bank transfers through Osko, have had almost universal contactless in store payments for years, etc. I suspect it's more about government corruption. Governments are captured, each for its own historical reasons, by different industries. Australia by mining industries, the US by medical & finance, local governments almost everywhere by property development.
It blew my mind going from that to what the US has.
The U.S. historically had many more banks than in Europe as the banking industry in Europe has historically been more centralized at the national level. Whereas in the U.S. not only did we have 50 states each regulating their own banking system (similar to Europe), but you had many more smaller banks rather than a few larger ones in each state.
It appears the U.S. now has fewer banks, but that's only because of a precipitous decline over the past few decades, and it's only been in the paste several years that the number of E.U. banks surpassed those in the U.S., long after the E.U. saw better payment systems.
So the reason the E.U. banking industry has more convenient payment systems, especially retail payment systems, is because they were historically both more centralized and less in number, which made consistent adoption of newer payment systems easier. Whereas the banking system in the U.S. was more fractured and far more diverse, and even with the dramatic drop in number and increase in centralization, we still see the repercussions.
FWIW in the US the banks are starting to play nice. They came up with Zelle, which is basically a federated payment processing system amongst the biggest banks to compete with PayPal/Venmo. You can instantly (almost, five minutes delay usually) send money to someone at another bank. The downside is that it is limited. Each bank has different rules, but it's usually just a few thousand a week. For example Bay Area rent can't be paid with Zelle.