Oregon. Not necessarily because the fields are slower than anywhere, but because there are race series 3 nights a week in the summer that count towards upgrade points in addition to road races and crits every weekend. The more you can race, the more upgrade points you can target.

Also, I'm not aware of any Cat 4 or Cat 3 lifers here that are winning many races. Sure, there are fast people every year, but most often they are in the next cat the following year.