Whenever China made its decision to lockdown the country (circa Jan 20), within a few days everyone started wearing masks. The first week masks could be a little hard to come by due to the heavy demand. I stayed in for 2 days then circa Jan 22 went out and biked around and the 3rd pharmacy I stopped in sold me a cloth mask with 3 replaceable filters. They also had surgical masks which they were giving out for free to folks in that neighborhood.
The next night I saw Xi JinPing on TV wearing a mask. A day or two later (Jan 24 or 25) some food stores started putting up signs saying Masks were Required for Entrance. Then I think that weekend it became standard to have your temp checked with a digital thermometer when entering grocery stores and big box stores.
So within a week masks became obligatory. Everything was closed down from Jan 21 except food / drug / big box stores deemed essential, and public transportation (subway and buses). I don't think mask wearing was actually mandated by law, but you weren't getting in anywhere without one. And compliance was extremely high.
I often viewed mask-wearing as a courtesy to others. A message that I was being careful and they were very unlikely to get it from me.
Anytime in FEB, the US should have started pushing mask use. And certainly by March 1 when there were a number of outbreaks spread out in the US. The GOP leaders didn't join the mask consensus until June 30/July 1, a full 1/4 of a year too late.
It's been shocking to watch the bumbling, belated, half-assed US approach to CV-19. Every step of the way the US has been way slow, way stupid, unprepared, poor in execution, devolving to local levels instead of a unified federal response. It's really been unbelievable. And it keeps on happening.
The Trump-backed reopenings have been disastrous, so he wants to double down by reopening schools. Lets hope whoever is still alive on election day votes agaisnt this Human Disaster.