@littlest-lily American culture is also terrified of anything that actual portrays non-traditional procreative sex in a positive light. Going back to Twilight, as a non-reader of the books, it’s always been my understanding that they were written from a weirdly moralistic standpoint.
As ‘kinky’ as vampires are, the relationship that Bella pursues with Edward is exemplary of monogamy and involves a very formal courtship process. The actual sex is problematized as the source of a dangerous pregnancy that Bella can’t terminate because the author is a Mormon.
Or maybe I’m thinking of Buffy, which also treats sex with vampires as bad not because it’s with a vampire but because sex has innately transformative properties: one moment of happiness for a ‘reformed’ vampire makes them immediately turn evil again, and sex is how that happens.
Most TV sucks at portraying this sort of thing well. The mark of a well-written show or series, IMO, is the subversion of these tropes. Twin Peaks is a great example, probably the best. True Detective does it well in a couple of seasons, too.