I've actually been thinking about something similar recently -- places other than Los Angeles becoming centers of the American film industry. I knew that somebody back then was looking at Flagstaff as a place to build a studio, but I didn't know it was DeMille. That right there is an easy POD. Have DeMille set up shop in Flagstaff, have him like the experience, and have him tell all his filmmaker buddies to head there instead of California. New Jersey also entered my mind -- partly because of Thomas Edison and his film studio, and partly because of local pride. Then again, the reason most of the filmmakers headed west in the first place was to get away from Edison and his control of the film industry. Maybe if you make Edison less greedy... which also has knock-off effects on Nikola Tesla's career... man, that could make for one interesting TL.
But, I digress. Let's get back to the original argument, concerning the film industry being based in Flagstaff instead of Hollywood. The Southwestern US -- and Arizona in particular -- becomes the center of American pop culture instead of Southern California. One possible butterfly from this is an increase in the popularity of Westerns, what with Arizona's closer association with the Wild West than Southern California. A bigger change is that surfer culture and, more importantly, the skater culture that emerged from it, will probably remain limited to the West Coast for a lot longer, since you don't have the studios in Hollywood giving it national exposure. As a result, the default "youth rebellion" subculture would probably be rooted a lot more in the "greaser" culture, the East Coast punk scene, and biker culture. The major figures in the industry (directors, actors, studios) would change due to the butterflies created by a new location, but barring some unforeseen revolution, the general trends are likely to continue happening on schedule. Somebody is going to come up with the film techniques employed by D. W. Griffith in Birth of a Nation or Orson Welles in Citizen Kane, even if it's not those directors or films. The Flagstaff film industry will still impose something like the Hays Code to avoid government censorship, and will replace it with a less restrictive MPAA analogue in the '60s as British and French cinema reaches American shores and tackles subject matter that the Flagstaff studios aren't allowed to touch.
Beyond pop culture, I can see Southern California becoming more conservative than in OTL, while Arizona becomes more liberal, going by the historical liberal tendencies of the film industry (it's no use to deny it -- and I'm a liberal myself). Arizona native Barry Goldwater may not emerge as a national figure under these circumstances, especially if you still have Joe McCarthy going against the film industry. Flagstaff will almost certainly be a much larger city than in OTL (maybe Phoenix-sized?), which would lead to greater demands for power and water, and most likely an earlier Glen Canyon Dam. Los Angeles will still grow into a huge city, as it was one of the largest manufacturing centers in the country during and after World War II, and was home to a large number of defense and government jobs. However, once the manufacturing sector starts leaving, it won't have tourism and Hollywood to fall back on, which means it's in for a huge fall.