They have started to appear in Austin, Texas, where I live, but only in the last 10 years. There are many more places they could be added, but I think when two

They have started to appear in Austin, Texas, where I live, but only in the last 10 years. There are many more places they could be added, but I think when two country roads meet you just make a plain "+" intersection, and as it gets gradually more urban it just never gets rethought as to whether it should be turned into a roundabout. But it is (where I live at least) slowly starting to get adopted.