Shifting gears: How do we shift people from private cars to walking and cycling?

That depends on location. As people keep needing to be reminded, there are plenty of places, especially in America, where you just can't bike somewhere. It is just the way the whole goddamn place is built, starting after world War II especially. The farther out you are from a dense urban center, the harder it is to bike anywhere. And that's not even getting into climate and weather. If you've ever had to ride a bike in the freezing cold or snowy conditions, or in 100°+ temperatures, you'd know that bikes aren't always the answer.