Even though you bring up a good point (can't argue with those numbers), but I bet if you look at the numbers 10+ years ago; I bet your numbers would be higher with Cali girls.
Most likely so, although not sure if that is due to overall numbers or just them being concentrated on the top teams. For instance, PAC used to have 4 teams in WCWS back then. I believe the sport has grown a lot over the past 10 years and every area is producing more top-level players since then. I'd bet the level of competition in Regionals and Super Regionals is higher now than back then.
With that being said, more northern states girls are making the jump to the organizations that has name to get into the larger tournaments where the top D1 coaches go.