It depends on your definition of "threaten", but the short answer is yes. I live in a mountainous area that's a destination for road bikers and mountain bikers. There's lots of sources of tension between cyclists and drivers.

On a regular basis I see people racing past cyclists, rolling coal at cyclists (I can't believe that's even a term now), blaring horns, and a number of other behaviors that fall under "threatening".

US vehicles, especially pickups, have outgrown a lot of rural roads that had their origins as footpaths and horse paths. Even with well-intentioned cyclists and drivers, it's often times a setup for conflict.