Roundabouts (or 'rotaries', depending on where you live) and yield signs could do a whole lot to reduce travel times and increase efficiency by a surprisingly large amount.
The problems are numerous, but mostly the urban areas weren't designed for such, the costs to switch would be large, and the American driver can take up to six years to adjust to a new traffic pattern.
Due to the rural/exurban character of the area, space for roundabouts isn't much of an issue. I suspect lots of other similar counties could do the same with similar results but it takes someone in the planning office to take the chance on doing it. Also it takes money so from a fiscal point of view, it's best to redo intersections when they're already scheduled for being repaved or they're having capacity issues that need to be addressed.
Perhaps ours are a different design?
Which makes them basically useless, and difficult navigate for e.g. vehicles with trailers--you end up running dragging the trailer over the center or something.
It can be depressingly long.