Can't speak for Braintree, but generally US-launched financial services take some time to expand internationally for two reasons: 1) tons of compliance and regulation unique to each country, and 2) having to interface with the specific payment technologies in that country.

PayPal is one of the best international payment options because it's had more time and money to throw at these problems than almost anyone else.

It's probably a combination of credit cards being far less popular in Europe (there are numerous local alternatives for online payment), and many of these services not being available to European companies at all.

i'm assuming it's the banks. perhaps they are less cooperative than US banks.

to most card processing gateways, their main source of bread and butter is their relationships to banks. technology comes second.