Times Square itself was mostly pedestrianized about a decade ago and a smattering of other cities have done similar things.
The problem is that the way postwar cities were built in North America has meant that the overwhelming number of people still need a car to get to the pedestrianized areas, so over the years most of them have failed.
I was going the comment that I wish American suburbs (even the inner-suburbs that are dense by US standards) were laid out in such a way that "Superblock" style redevelopment was possible.
The neighborhood in which I live (Reston, VA) was originally supposed to have several walkable "town centers", but all but two of them were built as standard strip malls, and one of the two that was built to original plan was demolished for a strip mall in 1994.
By happy coincidence, I can walk to work. But, grocery shopping is still a car ride away. And even if I could walk, I'd have to cross giant asphalt wastelands filled with distracted drivers.
Another case in point: Seattle has an outdoor mall called University Village. On a map, it looks like a walkable urban paradise but actually being there is a dramatically different story. There's a wildly-popular multi-use trail--the Burke-Gilman--that goes right next to the mall but direct access to UVillage from the Burke is not well-marked and involves crossing at least two roads. Access by bus is OK but you can tell that pedestrian access doesn't rank in the top five of priorities since one set of bus stops ends in three steps and the other set of bus stops accesses a pedestrian path that's almost always closed for one reason or another due to "construction."
Meanwhile, UVillage has an extensive set of interior streets with pretend stop signs for pedestrian crossings that drivers often ignore. And the mall owners keep building parking garages, closing off sidewalks for a year of construction in the process.
I have high hopes for the rebuild of Northgate Mall, on Seattle's north end next to a light rail station. The owners of Northgate filed their 129-page development plan with the city and they spend quite a few pages on how pedestrians will access the property, where people can congregate and play and exist without cars, and how the two additional interior streets will have calming and slowing measures to put pedestrians first. If the owners of Northgate Mall's written plans come to fruition as written, I hope UVillage's business will drop so they'll be forced to adapt in the same way.
The problem is that the way postwar cities were built in North America has meant that the overwhelming number of people still need a car to get to the pedestrianized areas, so over the years most of them have failed.