...keep in mind a couple reasons why they are news.
1. The media are not being banned from entering the country and/or being told to leave the country. In other words, independent reporting is taking place.
2. Britain and the U.S. have enjoyed decades of good political relations. In other words, Americans are sharing in the pain (so to speak) of a friend's suffering.
3. The issues behind the protest are understandable to an American audience.
The economic uncertainties in Britain and throughout Europe also help explain what is taking place, but the fear of unemployment or government malfeasance is not at the heart of these riots. They are peripheral; a claim of excessive force by police is.