Why no Black or Asian UK royals ?

Hmm, sort of. Those imperial ancestors aren’t all that distant. Some of the royals are old enough to have actually had an empire under them. QEII for example, was still a princess before the loss of India.
Would she not have been taught that she was in her position due to her racial superiority ?
Have they really moved on ? Hope so.

I’ll bet they do. Have the Japanese never had the sort of loss of empire and heavy immigration that made UK confront itself to a high degree ?

True enough. Are any of them even dating or flirting with non-whites ? Diana was the last one to do that, no ?

For the English, it seems to have been less racial superiority than national superiority.

The British royal family is heavily German, there isn’t even a lot of anything other than German and French there - go back ages to get Spanish or French. Prince Philip is a member of Greek and Danish royal families - both of them are heavily German.

Also, the definition of royal is pretty slim in the UK. Here is a wiki list. You pretty much need to be a direct male line descendent of George V to make the cut on a list today. British royal family - Wikipedia. So lets say that in 1740 you marry off Princess Caroline to a maharaja. (She died unwed and childless). Her children would not be British royals.

Until fairly recently they could barely marry anyone. George III put the Royal Marriages Act of 1772 into place. Royals were not allowed to marry all different kinds of people without the monarch’s express permission. So they mostly married fellow German protestants from certain families and that was it. Queen Elizabeth the Queen Mum was one of the few people allowed to marry into the royal family in 1922. She was an Earl’s daughter and from an ancient UK family but she was still seen as a commoner by the royals. Part of the reason she was probably allowed to marry the future king is because everyone expected his older brother to take the throne. No one expected the brother to abdicate to marry Wallis Simpson.

A Maori New Zealander married into the extended royal family:

I suspect World War One might also have had something to do with non-German protestants suddenly becoming acceptable :).

I also suspect the whole CofE thing is one of those archaic but still on the books laws, that would be rapidly be repealed if it ever became an issue with a future wedding.

No, it is a single country, but also a really big one. I daresay the regional diversity between New Mexico and Massachusetts is no greater than that between Cornwall and Yorkshire. Not geographically or climatically, but culturally.

Just a note on your specific example here - a few early Ottoman sultans up through at least Murad II did in fact marry Byzantine, Serbian and Bulgarian princesses, so not so clear-cut I’m afraid. All of these were European powers in either serious decline or effective vassalage of course, so the reasons for the marriages were fairly obvious - currying favor with the local dominant power.

I’ve lived in Cornwall and Yorkshire for years and there isn’t a great difference. They all have the same laws- they aren’t different states.

And a few women of the peerage married Arab men - Jane Digby being the most famous. They aren’t royals though.