I'd make them much more walkable, by blocking off certain short sections of streets from car traffic during certain hours. Many european cities do this, and it works well.
Adelaide has been building up walkable laneways that span the whole city to move in that direction. They are permenantly foot traffic only and they are hands down the best places to wander in the city. To eat outside is so nice when there are no cars shooting past, you don't notice how much noise they add until they are gone entirely.
I suspect that only works because those cities are already relatively walkable/bikable. Unless you live within walking/biking distance of the closed-off street, and the route between you and the street is pleasantly walkable/bikable, you are faced with the choice of:
1. Drive and park close enough to the closed-off street, and fight with other drivers for parking (very common experience around, say, farmer's markets in the San Francisco peninsula).
2. Don't go there; drive to the mall instead.
3. Walk/bike there anyway, putting up with the shitty/dangerous experience of doing so.
I.e., to apply this in the United States would basically amount to "redesign entire cities to be more walkable".