Some thoughts:
Ten lane freeways (not expressways) are not daunting, they just give you more opportunities to go faster. Finding the speediest lane...now that's a challenge.
In my experience, California drivers are not more aggressive than those on the east coast, but they do tend to drive faster. A friend of mine was talking about Dallas traffic to a resident of that metropolis, complaining about drivers not letting another driver into their lane. The Texan's response was: "You want in my lane, you have to earn it." Slowing down and blocking traffic in one lane while you try to get the balls to transition into another lane isn't going to cut it. I've found that to be true in California, and the east.
And then there's my most hated driving taboo: assholes who get in the fast lane and go slow. They're everywhere, but I've never encountered more of them than I have in Florida. That place is insane, with old people in their Buicks doing 55mph in the fast lane, and younger guys in their pick-ups weaving around them going 75.