California is a state, the state with the largest population in the US at over 39 million people. Of course it's going to top the list. It tops the list in everything. Because math.
The South, however, is a region, because it is not a state. It has more mass shootings than other regions.
Further, California is not just Los Angeles and San Francisco, much of it is rural farm country, and exceedingly Republican and Red. See it with those shootings spread out, and you get a different picture from the one you're pretending to show.
But wait, there's more. Other than those descended from immigrants, much of the population of California actually came from the Southeast, and they brought their renowned violent tendencies with them. They came in two waves, during the mid 19th Century (49ers) as well as during the Depression in the 20th (Okies).
California crime rates are not a result of this party or that party, it is the result of having a significant portion being the descendants of those who were brought to America as penal colonists from Britain back during the colonial era, people with a tendency towards violence and crime since before they arrived on our shores.