And most of those companies are low three-digit employee counts. I mean, I like King Arthur and tend to visit their store when I'm in the area, but it's only a relatively significant employer by the standards of Norwich, VT.

Why do folks think that is? Are there some US-specifics that make them less likely?

For example, the Mondragon Corporation, https://en.wikipedia.org/wiki/Mondragon_Corporation, in the Basque region of Spain is pretty huge (70,000 employees) and I watched a short news documentary about Mondragon and in general the employees there sounded legions happier than corporate drones in other companies.