It's not that subjective.
Checking the American Bonsai Society website, California has 35 clubs. Florida has 24. Pennsylvania and New York have 9. Illinois and Ohio have 8. Oregon and Michigan have 7. Virginia has 6. Arizona, Colorado, Hawaii, Lousiana, Maryland, Massachussetts, Washington and Wisconsin (!) have 5. All the rest have fewer than that. Some have none.
I'd assume the number of clubs indicates the number of bonsaiests. I also assume there are clubs in some states that have no affiliation with the ABS -- but not that many.