Apologies if this has been posted already. I found it sound and informative.
https://english.elpais.com/society/2020-10-28/a-room-a-bar-and-a-class-how-the-coronavirus-is-spread-through-the-air.html?ssm=TW_CC
If I had to guess, I suspect the recent surges (not just in the US) are due to relatively small, familial/friend gatherings indoors where all 3 measures in the article (masks, airflow, duration) are ignored.