Who owns the streets and sidewalks? If Main St USA is privately owned, who asses value and collects property taxes?

As a former policeman, here is the U.S. law. Public buildings are really not public. They are private for the use of the public. The rules thereby enacted by the managers of the buildings prevail. Just like the streets and sidewalks of a town are private for the use of the public. They are subject to the laws enacted for the town. Eg: behavior, parking, driving, etc.

Just know the law...