One of the biggest difference is walking. Most cities I've visited in Europe are easily walkable. You can more or less get what you need. People in small and big cities seem to walk much much more.
In Atlanta, this simply isn't possible for most people. We've built out more than up and inhibited public transportation but that's another sorry. Savannah is a much more walkable city similar to places in Europe. I wonder if it's the difference beetween old and new cities.