It’s transgressive and exciting and gets attention. It’s not white supremacy so much as the supremacy of those who benefit materially from uninhibited desire and are relentlessly selling it because it’s good for business.
Also, in the absence of taboos regarding interracial coupling, that primal virility of the black man makes the white man vanish from view.
As you say, advertisers and purveyors of popular culture are thrilled with the white woman and black man couple.
There are no institutions in America now that can effectively resist the purveying of endless liberation, which is really a form of enslavement and not liberating at all.
Interracial marriages have a much higher rate of break down.
Are white women, in general in modern society, more attracted to black men than white men?