Aren't you tired with that the most of games take place in US?
Reason for this is (unfortunately) simple. Voice Acting. Having recently (read yesterday) finished Sleeping Dogs, the one part that I disliked was that everyone was speaking english, throwing a few cantonese (I think cantonese, according to subtitle settings at least) every now and then. I can accept that the people that were talking to you were speaking english, since they knew you were away for a long time, but the random people on the street, talking to their cell phones? Or the vendor that you almost ran over, cursing at you in english?
Let's ignore for a bit the fact that not many gamers would be fluent in Chinese (may be wrong about this though), and assume the setting was in Paris. What would the person yell at you when you shove them, "You maniac!" or "Connard!"? What if the setting was in Berlin? How many Polish people yell obscenities in english when angry?
Thus, most easily accessible settings are English speaking countries, and preferrably ones the development and artists have first hand experience in. Add to that the fact that the US is a freaking huge country, and you can find almost any terain/climate you wish there, and that is a good reason developers like the US as a setting.
And just a footnote, I can't really play QfG5 without either laughing or facepalming whenever I hear the Greek words, including the ill fated Red Shirt.