The notion of trans-racial identity put me in mind of this science fiction story from 1973:
https://www.tabletmag.com/sections/arts-letters/articles/on-venus-have-we-got-a-rabbi
Anyway, comparing transgender and transracial identities, some thoughts.
I think there are people who may very well identify, in a very meaningful way, as a different race, but I think it's different from people who identify as the gender not associated with their sex.
There is no conclusive, definitive, explanation for transgender phenomena, but a lot of scientists who have studied the phenomenon feel that there is an actual medical explanation. There is some evidence that hormonal fluctuations during pregnancy at certain key times can influence fetal development and cause someone to identify as the "other" gender.
In order to believe this, the only thing that we need to believe is that some behavior is inherently sex-biased, and that we have an instinctive "knowledge" of what it means to be male or female. I put "knowledge"in quotes, because it's not exactly knowledge, but I can't think of a different word. You have to believe that somehow, thoughts and behaviors are instinctively associated with being one sex or the other, and that there's a developmental pathway that causes the behavior patterns and even the thought patterns to develop, and that development is correlated with sex. However, you also have to believe that something can "go wrong" or "get crossed" or something, so that the psychological/neurological elements go a different route than the physical development.
None of that is implausible to me, and a lot of people think that's what happens. A person has male genes and develops male anatomy, but there is something that influence our own behavior and thought, and that can go down a female pathway.
That's a transgender person, at least if the theory is correct.
I don't think there's any support for a similar concept of "transracialism". I don't think there is "knowledge" of what it means to be an African or a European. I don't think that's instinctive.
On the other hand, the general concept of a tribal identity I think is, in fact, instinctive. In other words, I think we are "programmed" to associate with people of our own tribe, our own racial group. I think appearance plays a huge role in that. i.e. I am more likely to think of people who look like me as part of my tribe, and I think it's instinctive to behave differently toward people of your own tribe. However, the tribal identification aspect also has a huge cultural component. It might not be just people who look like me, but people who dress like me, or even just people who live in the same place, or, very importantly, people who work together in shared activities, like a sports team or company or army.
So, a person could have European genetics, but if raised among Africans, he could very well think of himself as an African. It seems to me that he would even be right to do so. Of course, he could easily tell, from a very young age, that, genetically, he must be different from the other members of his tribe, but nonetheless he would still identify as part of his tribe. That would be a trans-racial person.
So, I think both transracials and transgenders can exist, but I think one of them is caused by culture, while the other one probably has an underlying associated medical condition.*
*ETA: In many cases.