Yep, that one! We have a lot of regulars, and even people (non-American) who come in every.single.day. There are quite a few Americans working there; I'm one of six, but I only work the morning shifts (until about 4 or 5) for the past 3 months. So depending on when you've come in, we may indeed have crossed paths. Say hi next time! 
I've definitely been there every single time I'm in London! I love Chipotle. It's the only fast food place I'll go to.
I'm in Edinburgh, next to the university and just south of the Royal Mile, so hearing an American accent is an everyday occurrence for me. In fact, there have been times when I walk from my flat to my local Sainsbury's, and I hear nothing but non-British and North American accents. I'm asked for directions quite a bit by American tourists, and they're always shocked to hear my accent. They're also a bit apprehensive about taking my advice until I tell them I've lived here for over 3 years and live nearby.
When I first brought my husband to visit my parents in Colorado, my mom told my husband he'd have to meet her friend's daughter-in-law, because she was from Cambridge. I think people assume that because you're from the same country, you will all get along and want to meet each other.