I am not sure - is it the density or is that herd immunity is already partially in California and that is why it has less than California.
I have wondered if the country could have developed herd immunity having everyone wear masks. Doing so would not protect entirely, but it would reduce the viral load every one exhaled and inhaled. Masks hopefully help in building immunity without an overwhelming exposure to a huge viral load.
Those with medical issues and the elderly could still be quarantined, and making special programs to make isolation more tolerable.
Can anyone explain why Fauci and the rest of the experts has not discussed this?