There's a similar situation in Switzerland, where a handful of banks dominate the national market despite some smaller (cantonal) options that mostly have their own consortium anyway. The larger banks cooperated on creating a mobile payments platform known as TWINT [1], which allows for fast and free individual payments for splitting the cost of a meal, private sales, or even many in-store transactions. This allows them a competitive advantage over alternatives such as small Swiss banks or foreign banks that the many non-Swiss residents in Switzerland may otherwise continue using. These other options are relegated to IBAN transfers which are notably less convenient.

[1] https://www.twint.ch/en/

I think the problem is less the country size and more that the USA had a legislative structure that encouraged small, local banks until recently (1980 iirc) and so before then there was a Cambrian explosion of banks (pardon the pun). Now banks are gradually consolidating, but they have nothing close to the oligopoly that you see in countries without that sort of history.