Some European ones because the domains have European TLDs. .eu for example is only available by EU registrars IINM. But also, I do my best to keep the money local where I can.
I don't think that's true anymore. I moved my .eu to porkbun (which is an American company) and it works. Also, I just tried registering a new .eu domain with them and it works - and they have very good prices! (I'm not affiliated with them)