State fatalities per 100K population depend on both the case rate--victims who have had the disease--and the case-fatality rate--deaths per case. And case-fatality rate is highly dependent on the age distribution of state population.
At present, there isn't a lot of difference in case rate among the states mentioned:
There is a greater range in case-fatality rate:
The combination of those two is the fatality rate (very close to the numbers previously posted, but from source cited below):
As seen above, the case-fatality rate has a larger effect on fatality rate than the case rate. And much of that difference is explained by a difference in age distribution, since the elderly are much more likely to die if they contract the virus than the young. California population age distribution is distributed with the COVID data; I didn't try to find population age distributions for all of the states, but I did find Florida easily:
So Florida has a proportion of 65+ residents one-third greater than California, which will have a significant effect on case-fatality rate. In California, the case-fatality rate for 65+ is 25 times as high as the < 65 case-fatality rate. Assuming the same age-group case and case-fatality rates, California deaths would be 20% higher than they are if the state had Florida's population age distribution.
For the record, those southern states are not the COVID hotbed some might think:
Case and fatality counts from the
COVID Tracking Project.
California age distribution from state
Department of Public Health.
Florida population age data from the state
Office of Economic and Demographic Research.
.