[ido]

I don't know how you use "boutique" in the US, but it's a commonly used word around here (when speaking English anyway).

I do think there is definitely a qualitative difference in the way people speak in Europe and in the US (also when speaking languages other than English).

I was a bit surprised when I have heard a (supposedly, could have been Canadian AFAIK) American tourist saying something like "they were just a bunch of dudes hanging out" (she was a woman in her 40's, in Austria using an equivalent form of slang is something normally reserved to much younger people).

[jumper]

It was always amusing to me when my British drama teacher would use a word that Americans rarely use like "coach" or "metro" (as opposed to bus or subway). I had just big enough a vocabulary for it to be no effort for me to understand her, even if I never used such words personally, whereas everybody around me just went "huh?" I guess I'm finally noticing the times when I'm on the other side of that divide and have to really think about what the unfamiliar words mean in the given context.