How hard is it to transfer or switch to a bank in Europe from the US?

Switching Offices depends on the following:

1) Your performance at work. Bad performers won't have a shot at switching.

2) Bank culture and group culture. Each one will be different. Group culture is important because if your managers are pissed they'll lose you, a spiteful manager might make it their mission to prevent you from switching.

3) Communication. Bring this up subtly to your manager ex:"Is it possible to ever switch regions to get exposure to a different culture,etc". This will help you in gauging their interest in helping you with this endeavor. Try to network with bankers/MDs from that office so that they know your name; if you can get an MD that likes you in your current office to vouch for you that'll be very helpful as well. You should also talk with HR but phrase your discussion to be an informational one and that you're looking to learn about the process. One thing you want to avoid is having HR reach out to some senior people about a potential switch before telling them yourself. However, if you work with a bunch of assholes, I wouldn't advise telling them before going to HR.