Part of it, probably, is that American culture tends to elide the details of a lot of traditional stories. Not to censor it, necessarily, or bowdlerize it, but just to de-emphasize it and not go into much detail. Whereas Dahl really does have quite a bit of gruesome detail. And then part of it, probably, is that Dahl is kind of dark and pessimistic and bitter a lot of the time.

I don't know. It's honestly really hard for me to see him as anything other than a dark macabre weirdo. And I really liked his books growing up. Maybe it's a cultural temperament thing where Americans are more sunny and optimistic so the bitterness stands out more? I usually hate that kind of explanation but there you go.