As in your comment you mentioned porn, let me focus on that. What i am going to say refers to "heterosexual porn" only, so doesn't include gay.
The U.S. were and still are the biggest porn producing country with a worldwide share of close to 40% of all porn productions.
Let's recap how that industry has changed from "old school porn" to the current "state-of-the-art" industry. There are plenty of differences between those two.
First "old school" was more concerned with American customers than a foreign audience. While this holds still true for the most part at least some of the production companies have become more diverse in order to also appeal to customers from foreign markets.
"Old school" rarely did research on their customer's needs, if they did at all. The themes they were portraying were mostly or solely based on assumptions! The "state-of-the-art" investigates deeply into customers' likes and preferences, easily done via first-hand data gathered by site analysis of porntube sites (what is being watched, what is being searched for). Also current production firms know much more about their customers (sex, "sexual orientation", age group, ...)
To understand what normatives "old school porn" pushed we need to look into their assumptions:
* produce for the
mainstream because niches have a higher risk when it comes to sales
* the typical porn consumer is male (Women do not watch porn. - An assumption proven false by now, like most of the other assumptions below)
* the target group of mainstream porn is the white American man (of course! more than 3/4 of the American male audience is white, only a bit more than 10% are black)
* porn consumers are mostly interested in watching Women they find attractive - more generally put "feminine" Women
* the feminine paradigm is defined as the opposite of masculinity (i.e. no muscles but big boobs, and preferably short body height)
* if there is a man in the scene, the consumer seeks to identify with the male for his fantasy of being there with the gal instead of the performer
* the consumer does not want to see male performers who would intimidate them by their looks as they don't want to feel outcompeted by the other male
All of that led to decades of porn featuring short fake-boobed Women of all colors masturbating, playing with each other, or having sex with a white male performer who is far from being a hunk. (Because that was the mainstream paradigm of the ole days.)
Look at the Black female porn performers' statistics of (boy/girl) scene pairings both in the old days and latter-days of porn and you will find that on average those have 80% to 90% scenes with white guys while no more than 10% with Black guys typically.
Of course "black-on-white" (meaning Black male with white female) porn always existed. However it was less available in the ole days. It was a niche you had to look out for in particular and you should have known where to look because you didn't find that easily in a catalogue.
i believe that "black on white" lacking in the market for decades is the reason it has become sort of a social antithesis to the past among porn consumers. Because it was rare it has become special. And now that it is greatly available it is what people are looking out for - it's high in demand. The same is not true when it comes to "white on black" porn because it has always been there in reasonable high numbers.
Just my two nickles worth.