In the 20th century The Western was the most dominant film genre. How can we prevent its rise and what other genre's could replace the western as the cultural icon of the 20th century?
Make pulp western books unpopular so that the public does not have an appetite for westerns when film comes around.
Also have western films be prohibitively expensive to make instead of one of the cheapest to be filmed.
That would be difficult due to the film industry being based in the Southwest, a perfect place to shoot stories set in deserts. Maybe have New York City become the base of the movie scene instead?