There are 13 states that subscribe to the California requirements. I live in Mass which is one of them.
I also believe the cars are all exactly the same and the reason that they put a California sticker only on those cars that are being shipped to the 13 states that subscribe to California requirements has to do with certification fees that have to be paid to CARB for each approved car sold.
My 13 Focus ST came with a non California sticker. A few months after delivery I got a letter from Ford with instructions to cover the existing sticker with the enclosed California sticker.
Dave, I believe you and the others posting similar views are right. I pulled down some FMC emission certificates and they are different. One is for CARB and lists emission results and the other cert is just an EPA cert stipulating conformance to the clean air act.
Besides the nominal fee that might be tacked on, there are subtle differences in the emission warranty coverage for both.
I would have to conclude that there is none to minimum performance impact on what certification accompanies the car with the exception that the gasoline formulations in locations with tightly controlled pollution levels may have some impact.
The charades with the certifications is a mystery to me because you can still bring in a new car to CA from out of state after the prescribed wait time of 7 months I think and get it certified at a smog station and register it in CA.