Hmm ...

... In the Wake: Per Petterson and the Notion of Contemporary Existentialism | Quarterly Conversation.

... it is fair to argue that America has never, truly, produced an existentialist writer worthy of the term. Our closest attempts can be seen in the works of the Lost Generation, the suburban masters of the 1950s, and in Carverite minimalism of the late 1970s and early ‘80s, but even at their best they lack a certain je ne c’est quoi that permeates Kafka or Kundera or Beckett.

Maybe it has something to do with the American temperament. And also with the fact that, as often as not, an "existential" novel uses fiction as a means to an end rather than as an end in itself.