They have obscenely huge streets and drive like lunatics. They place a high premium on self-expression yet have less worth listening to than an accountant from Nebraska. They have a cartoonish view of the rest of America rivaled only by residents of New York City. They're the only people from anyplace in the world I've ever met who can be both laid-back and uptight at the exact same time.
I moved to California from a Chicago suburb when I was 19. The shock and dismay of that foreign culture, back in the mid-80's no less, will require one or more posts here someday. Or maybe a book.