Or, perhaps you're mostly surrounded with white men and women? I know I am; Sweden is predominantly white-skinned people, and all the trans-people I know of are also white-skinned.
I saw a video a couple of months ago, with trans people sharing the experience of having being treated both as men and as women, and that women definitely had it tougher. In that video, there were both white and non-white people, as far as I remember. They spoke English, so they were probably Americans or English people.
How could it have been learned? Who taught them? Their parents are usually in shock and refusing to believe it when they first hear their child saying "I'm not a girl, I'm a boy" or "I'm not a boy, I'm a girl", or “I’m not a boy nor a girl”.
It's not something they believe, dearie, they KNOW it, usually from a very young age, that something is different about them. All signs point to them being born with it, whatever "it" is. Brain sex and body sex apparently develop at different times during gestation, and in rare occasions, the sexes of brain and body don't match. There are also the people born with neither XY nor XX, but with another combination, and there are those who are born with XY but never changed from female to male in the womb (we all start out as female, that's why boys have nipples too).