Well obviously it couldn't really work in America (although I guess if traininthedistance reads this he might crack down on my head for saying that). U.S. cities are too sparsely arranged (I pity the urban planer trying to work LA into a remotely usable city for non-motorists), zoning is too weirdly arranged and public transport routinely underfunded. But it would be interesting to see if the Oslo-dwellers (oslonians?) can figure out a way to make it work. A lot of European cities weren't really designed for the car, and you can ... tell.
FUN FACT: When Norman Mailer ran for NYC Mayor in 1969, one of his campaign planks was making Manhattan car-free. And Roosevelt Island was actually car-free for many years, though they eventually gave up on that.
But seriously, while it might be nice for some small areas like Manhattan south of Canal, or downtown/North End Boston, and while there are certainly individual
streets where it might make sense to remove auto traffic, this isn't something I particularly care to push. I mean, cars can drive on woonerfs, they just can't put their speed over other users' comfort and safety. It's more important to tame them/build dedicated infra for other modes/make them pay their social costs over a wider range of urban areas, then it is to merely have symbolic car-free centers.
Though seeing cities across the pond do it is good if only for the aspriational/rhetorical effect, and it obviously
is feasible over there, so FD.