I think they can also solve quite a few suburban problems. There are many examples of other countries whose suburbs are connected via public transit. And many trips can be done via bike instead of car.
Yes, but American suburbs aren't like other countries' suburbs. British suburbs, for example, are much denser and usually very walkable.
There are a few American suburbs that are well-walkable and still support automobile transport. They're just not engineered to _only_ support automotive transport. We've had them, then destroyed them.