The very worst I've seen in the US were in Miami, Florida. I drive in Vegas a couple times a year, and I don't think they're as bad as Portland drivers. Seattle isn't as bad as Portland, either.

The worst, period, were in Cozumel, Mexico.

The best, and most courteous drivers I've seen were in some of the smaller towns on the dry side of Oregon and Washington, and in the more rural areas of most of the western states.

But let's face it, if everyone drove as well as we do, we'd all be just fine!