Most all of Missouri is under a mask mandate. Just not state mandated. There are some rural areas that are not under them, but most all of the cities of fair size are.
Not sure what you mean about control but enforcing compliance in a public building should be easy. And at least around here some businesses have been closed due to non- compliance.
This is sort of a vague study. Tennessee apparently has county wide mandates and they compare counties with no mandate vs. Counties with mandates and make that comparison.
And the counties with mandates show better safety and less infections and spread. Which makes sense.
But there are states with mandates, like Michigan, that is seeing significant growth right now. Where we are seeing the growth, though, is in young people and rural areas, where before it was mostly urban. This, I think, has more to do with the fact that rural areas were not hit before for the most part and now they are. And rural areas tend to be non-compliant with the mandates. In Western Michigan and Northern Michigan folks were throwing huge parties and generating clusters of infections but they were mostly outside. Now they are inside and the infection is raging where before it was limited due to parties and gatherings being outside.
Colder areas of the nation are going to spike because we gather inside now, if that area has high mask usage (like urban ones) the spike will be limited and if it more rural the spike will be bigger. Masks would definitely help rural communities fend off this wave but they have been non-compliant so long I am unsure if they will adapt.