In this day and age I just assumed you couldbe whatever you feel like on any given day and use the bathroom that most closely matches your feelings on that day.
Unlike your gender, your race/ethnicity/origin is just kinda a cool thing. none of that **** actually really matters that much, it's more of a curiosity. some people put too much stock in being one race or the other, as if being a certain race or having a certain amount of blood imbues a certain characteristic from that race or blood. We're all from the same species. Being 1/8 Japanese does not give me superb math skills, and being Irish doesn't help me hold my liquor down.
Gender on the other hand is different, because the deviation in certain physical characteristics is substantial.