Most American suburbs with no sidewalks (though lots of them do have sidewalks and bike trails/lanes) have streets that are so low traffic that you can just walk in the middle of the road (or on the grass if you prefer that). The major roads tend to have sidewalks and/or bike lanes. The same people who attack American residential roads applaud similar streets in Europe.
The first thing urbanist groups pass are
urban growth boundaries which make it illegal to build new houses. They also like to tear down roads and make it illegal to build parking. In most of the US, there is nothing stopping an urbanist from buying some land and building their dream car free high density neighborhood, but they aren’t happy with being able to live in a place they like; they want everyone to live like they do.