In reading the comments, I'm actually surprised no one mentioned this: the story would not have been believable had it taken place in flyover country.
I've never heard the term "flyover country"--that's an interesting one. But not everyone in the center of the US is gun-toting. Though hunting is common, and some people do carry their hunting guns in their car, far from everyone would. And this may surprise people, but there are actually cities in the Midwest--it's not all gun-toting farmers.
Fenrix explained the term well. I use it (as others do) to remind people that there's this big place between New York and Los Angeles called "America" - haha. I was not, as Fenrix possibly insinuated, using it as an insult.
I was also not implying in any way shape or form that everyone in the midwest is a hick farmer straight out of a Jeff Foxworthy joke, I was only implying that in a crowd of that many people on the freeway, in many states other than CA, there would be at least one person with a gun willing to help. Again: not everyone, but there would be a couple most likely. For example: in 1997 in Mississippi a Columbine-styel massacre was stopped by Joel Myrick and his .45, while in the same year in Edinboro, Pennsylvania (not flyovercountry, I know, but not CA either) James Strand convinced a teenage killer to surrender by brandishing his shotgun.
I'm not here to make a gun-control case one way or the other, only pointing out that versimillitude wise, CA was a good choice.