The local TV market (which also covers OC) has a college football fan base of about 2.6 million, or 17 percent of the population, according to calculations by the NYT's Nate Silver (how does he come up with this stuff?). That compares with 41 percent in Atlanta, 30 percent in Tampa-St. Petersburg, 28 percent in Houston, and 27 percent in Dallas-Fort Worth. (Birmingham, Alabama is at a frighteningly high 85 percent.) Actually, L.A.'s fan base is considerably bigger than other markets in the West, which leads to Silver's other finding: Pac-12 teams, including a powerhouse like Oregon, are not especially popular, based on the number of fans. If you ever wonder why Western teams will sometimes get the short end on polls and such, this could be a good reason.
The Pacific-12 plays plenty of good football, but the low avidity of college football fans in the Western United States means that it's in the second-tier as a television product: only U.S.C. and U.C.L.A. have at least 1 million decided fans each. Despite their strong performance on the field, meanwhile, Washington and Oregon rank outside the top 40 in terms of their fan footprint. And other conference schools, like Oregon State, Stanford and Washington State, do poorly by major-conference standards. As compared to these teams, new additions Colorado (0.5 million fans) and Utah (0.4 million) look tolerable -- but their fan bases are likewise middling by national standards.
As you can see, only USC and UCLA have fan bases in the top 25.
All of which is a reminder that the L.A. market is vast and diverse - and football, be it college or pro, comprises a relatively small part of the pie.