Most of the radicals seem to be in the House Of Representatives, but the majority of Americans are still pretty sane. It is because the districts of those elected representatives are so gerrymandered that they get into office. Plus, most people do not like voting in non presidential elections, for what ever reason. If more people would vote in off year elections, then maybe we could keep some of these radicals out of office.
Yes, the radical era appears to have passed in the United States. The era of open protest, which began in the 1960s but petered out by the end of the 1970s, was a time when people brought real change to society. However, even with the Occupy Wall Street movement, there seems little inclination among the majority of Americans to protest.
I think that America can definitely be described as "post-radical". While there are still a lot of individuals who continue to portray that the idea of radicalism is still alive and well in America, I think for the most part, it is not something that is as evident as before.
Assuming by "radical" one means actions against the state or corporations that are inclusive of destructive acts then America's current lack of such actions is not as much the proximate cause of a social shift in values, but rather the result of effective evolution of policing force capability in crowd control methods.
Today's America cannot be described as "post-radical." This is because today's America is very radical. There are many people who sympathize with radical sentiments, such as open borders, anarchy, and free love. These issues are hot topics and accepted by many college students, and young people are the rulers of the next generation.