I am sure the virus was here well before we realized it. By the time you find your first confirmed case it is already too late. It still doesn't really explain the low numbers. I think the numbers being lower than New York have to do with how the people responded. In NY Cuomo has literally scolded people on TV for not taking things seriously in NYC. People still hold gatherings, they still crowd together in parks, they are crowded together on public transit more than in CA. There are many factors in play.