we have a very wealthy (by world standards) very mobile society with HUGE metropolitan areas crowding a lot of people in a little space. We also dropped the ball on early testing and social distancing measures in those metropolitan areas.
Look at the numbers in metro areas versus the rural areas. Look at New Orleans post Mardi Gras. They are now the fastest growing area in the country virus-wise.
People need to practice common sense. Unfortunately, a lot of people now are sadly lacking in common sense.