What fell out of 1968 was a profound division over what I would call civic vision. One side...concluded from Vietnam and the race riots that America, in its relations with the world and its own citizens, was flawed and required big changes. Their defining document was the March 1968 Kerner Commission report, announcing "two societies," separate and unequal. The press, incidentally, emerged from Vietnam and the riots joined to this new, permanent template.
The other side was, well, insulted. It thought America was fundamentally good, though always able to improve. The Voting Rights Act passed in 1964 on a bipartisan vote, opposed mainly by southern Democrats. This side's standard-bearer called the U.S. "a shining city upon a hill." But after 1968, no Democratic presidential candidate would ever speak those words.
Read his article, there is lots more there and it is all good. His summary of all the ugly stuff that happened in 1968 is amazing - what a tough year that was.