I very seriously doubt anyone will care and chance are it will go unnoticed. Assuming your birthplace you wrote down is recognizable as a US location, I'm sure they'll figure it out easily enough. For example if you put Alexandria VA, no worries, if you put "Cambridge" they might not know whether its Cambridge MA or Cambridge England. In the latter case I'd send a note to the adcom to clear up any potential confusion. Either way it won't affect your admissions prospects imho.