I would be shocked if even half of the American workforce primarily works in an "at a desk" or equivalent type position.
I'm curious about this but don't have time to look up numbers. It's hard to make a reasonable guess because while cities (and the offices within them) have the highest density, there could be a very long tail of factory, strip mall, grocery store, etc. jobs that would be higher per capita outside of cities and invisible to someone living inside a city.
Even in a city you're completely surrounded by people who don't have desk jobs. All the people who deliver stuff to your office, the maintenance staff, all retail and restaurant employees, law enforcement and fire/EMS, taxi and car service drivers, and on and on and on.
And that's just what's in an office district. Drive down the NJ Turnpike or something and count how many massive employment centers you see that are primarily not office jobs. Everything from the shopping mall to the refinery to the airport to the distribution center.
I'm curious about this but don't have time to look up numbers. It's hard to make a reasonable guess because while cities (and the offices within them) have the highest density, there could be a very long tail of factory, strip mall, grocery store, etc. jobs that would be higher per capita outside of cities and invisible to someone living inside a city.