[mikeash]

I get what you're saying, but "hola amigo" is a really bad example of it. There are 40 million Spanish speakers in the US and tens of millions more use Spanish phrases routinely as a personality quirk. "Hola" and "amigo" are both words that I'd expect most Americans to understand, and I wouldn't bat an eye if a CIA agent greeted my in that way, assuming the context wasn't too formal.

Maybe a better example would be... well, if they put their hand over their heart and said "salaam habibi" to an American scientist.

[mason55]

Yeah, maybe I watch too many movies, but "hola amigo" feels like a totally appropriate greeting before you're about to do some shady spy shit. I think that it's actually a good greeting because it indicates to the other person that this interaction is about to be a bit informal.