I do a fair amount of travel all over USA (and Canada).  I have come to the conclusion that for what ever reason (distraction, self importance, ignorance etc etc) the main reason for 99% of the frustration I find on all roads is due to a general lack of curtesy.  So maybe you did not break a law by cutting me off, or pulling out in front of me a little close, or by driving slow in the fast lane etc etc.  You still are effecting me and others with a lack of curtesy.  If people walking down a crowded sidewalk acted the same way they do while in a car they would get popped in the face 100 times a minute.

Just think of most if not all the driving laws - they are based on curtesy.  Signaling your lane change or turn, Yielding right of way, speed limits, tailgating, passing........

We've simply become a bunch of self important, self absorbed jerks when behind the wheel.