[fastball]

The reason for that is because the US was "standardizing" finance before the EU even existed, and therefore has momentum from those standards that needs to be overcome in order to adopt new standards.

e.g. having strong anti-fraud/anti-theft practices built around signatures.

[pgeorgi]

European countries were also standardizing finance before the EU existed, but that meant that there already was the infrastructure of banks working together (in each country) that was then used to establish the EU wide protocols.

In comparison US banking seems rather adversarial in nature and so there are few interbanking standards which led to the need of a layer on top in the form of credit card companies to abstract away the differences.