So you're just going to ignore all the examples that are found in Europe where it does work?
Road traffic is bad because the majority of commuters in the US take up 50 square feet (or more) of road space for one person. AKA, one car per person. Robust public transport (busses and trains), plus mixed use zoning (you can walk from your home to most where you need to go) are how we solve the problems US cities face.