Hong Kong is fucking awesome to get around. Why not moving sidewalks like they have there with the Midlevels Escalators? I used that to walk from Midlevels to Central every day and loved it.
The United States has a population density of 35 people/km2.
San Francisco has a population density of 7,124 people/km^2.
I'm not sure what point you were trying to make, but I don't think anybody really wants to plan the rural areas of the US in the image of Hong Kong.