From my experience, South America, Africa, and the Middle East have horrifying traffic behavior, but at least everyone follows the same unofficial rules of the road. Eventually, you can somewhat reliably predict how someone on the road will behave.

Different areas in the US have very different driving cultures, and the transient nature of the DC area means that drivers bring their habits from wherever they came from, and so everyone is obeying slightly different driving cultural norms. It's a mess.