I think there are a few things that need to be taken into consideration. (you'll have to excuse some of my examples if they aren't 100% correct or p.c.)
#1-The DMV will give a dirvers license to pretty much anybody.
#2-Unlike many countries you are not required to be able to read, write or even understand the "prominent" language to receive a D.L. (the D.M.V. here in Portland has something like 12 different language options for individuals looking to get a license).
#3-America is a cultural "melting pot" You have everybody from the courtious English "Gent" who'll give right of way, use signals etc to the former Saigon taxi driver who doesn't know what a turnsignal is and will drive down the wrong side of the road simply because it suits them.
#4-Many U.S. citizens think that they are entitled to certain things, actions, behaviors etc. The idea a lot of people have that they are important or special and that everybody needs to pucker up and kiss their rosy a**es. Even individuals who have done absolutely nothing usefull in their life think that they deserve special treatment and that whatever they have going on is the only thing that matters in the world even if that thing creates an enourmous inconvience for anyone/everyone around them.
I'm gong to stop now but yeah, I agree, there's issues.