This article gives one of the best descriptions of the struggle surrounding Expat relationships that I've seen.  I'd go even further, though, and say that even my friends here who are fluent English speakers wouldn't see me as the same person as my American friends.  I've become much more cautious with my language, and even jokes can be suspect because of the cultural differences.  I laugh and joke with my friends in Chicago in ways that I never would with (my few) friends here.  I'm a much more reserved person here than in the U.S., not that I was ever that loud to begin with.