We've gone back and forth among the the three states for so many years now that there's not really any question about what we see. The driving cultures may shift over time, but they are real. If you saw the painfully polite drivers in Oregon you'd see my point.
California drivers historically are both aggressive and on task. Utah drivers are historically aggressive and distracted. It's not just turn signals. They also don't look at cues of other drivers around them as much. They just drive in a bubble. Obviously not everyone, in any state. But there are driving cultures and Utah's driving culture is kind of dippy.