Superheros are mostly an American obsession. They never really caught on big in Europe.

Also, a lot of the books and authors you mention there happen to be British, so there might be a natural domestic content guideline influencing B&N's decisions on what to push in their stores.

Superhero comics have influenced a lot of anime and manga, and vice-versa, but American superheroes as we know them here are not big in Japan, as far as I know.

Our stores usually carry Sandman, Hellblazer, Transmet and stuff like that too, but those are all published by DC or DC/Vertigo and fall into genre's "adjacent" to superheroes.

Do you get the Queen & Country over there? It's among my favorite series. It's about British secret agents, but it's written by an American.