Pix, UPI, etc are nationally silo'd and have little risk of spreading around the world. They took over their respective countries because they were government backed and mandatory.

The US has its own version of this: government backed, 24/7 instant settlement payment rails (called FedNow). It released in 2023 but adoption is slow because it's not mandatory. Banks are especially slow to support "Requests for payments", which might compete with card networks for retail purchases.

It's the banks, not Visa / Mastercard, that make the most off credit card fees. Visa / Mastercard take .1-.2%, the bank takes ~2%.

The other unique bit about the US is we have uniquely strong consumer protection laws and a uniquely large amount of fraud. Irreversible payment rails are a nightmare for consumers who are used to chargebacks being built in to the payment rail, and banks are skeptical of exposing such rails to consumers because most of the time the banks are required to make good when the customer is defrauded.