The Writing Room is generally filled with aware people from around the world. I dont know anyone regularly on the board who would have menationed "Murrica" or American sunglasses. Stating the "Americas" and leaving it at that would have been suffient--especially since you're naming other continents at the same time.
I'm of the writing mind that the author decides where the stories are set. (But i also think the author is the puppet master of the characters.) Frankly i dont think my opinion on such things should matter. This is especially true if I'm not the target audience for your work.
~Raging and quivering female mass of hormones and tosser of Dark Side Cookies™ (trade marked by Etoile)