This is overstated. At least as of 2017, Americans walked about 93% as much as people in France, for example, and a little more than people in Portugal or Greece.
https://www.statista.com/statistics/747380/daily-step-averag...
https://www.statista.com/statistics/747380/daily-step-averag...
The difference is: they COULD walk if they wanted.
You can't if there is no walkway.