Exactly, "in USA". That's where the "only popular in a single region of the world" part comes in.
Trucks, especially the variety seen in the US, are practically unheard of anywhere else in the world. When a specific style of vehicle is that popular in a single country it probably has more to do with legislation than driver preference. There is almost certainly a decent portion of people driving trucks who would prefer an alternative form factor - if only it were available. It'd make sense to distinguish "truck drivers" from "people driving trucks".
Trucks, especially the variety seen in the US, are practically unheard of anywhere else in the world. When a specific style of vehicle is that popular in a single country it probably has more to do with legislation than driver preference. There is almost certainly a decent portion of people driving trucks who would prefer an alternative form factor - if only it were available. It'd make sense to distinguish "truck drivers" from "people driving trucks".