There are plenty of examples of structural change taking place in the US since our founding that did not involve the Federal Government raining down violence. Most of these examples involve state governments raining down violence with the Feds stepping in to stop them. The most obvious example is the Civil War, but it carries through the New Deal, the Civil Rights movement, anti-war protests, etc. The main example of the Feds perpetrating such violence is mainly against the Indians in the 19th c. See, for example, Andrew Jackson's famous, "John Marshall has made his ruling, now let him enforce it."

Another moment of structural change is inevitable, and it looks closer to being a necessity all the time. It will happen through the ballot box, however. It might not look like much, but even getting the ACA passed was a coup. It shows that progress is slow, but can be effective. I don't know how our tax system will get reformed, but that will be the next big thing. One reason I couldn't support Sanders fully (although I did vote for him) is that his ideas may not even be better than the status quo. We need young blood to put forth new ideas. Until that happens, I'd rather stick with the devil we know.