Gist: Every week (until travel from China was shut down in Feb) thousands of people had direct flight from Wuhan to four California airports (San Jose, San Fran, Sand Diego, LAX) during Nov, Dec, Jan. CA had a spike in flu-like cases during those months, but many tested negative for the flu. It is possible that the virus already ran through the west without anyone realizing it, and the social distancing measures in place are not the reason for lack of current spread.

Until they do widespread testing for antibodies we will not know for sure. But it is basically impossible for CA to not have widespread infection, even with social distancing, yet here we are.