When did the U.S. lose its 'innocence?'

Continuing to discuss the Las Vegas massacre, a panel on the Scarborough show this morning took up the old refrain about America's loss of innocence, which at least one panel member dated back to the assassination of President Kennedy in 1963, the idea being that the ability of a loser like Lee Harvey Oswald to take down the most powerful man in the world made the killing an unprecedentedly demoralizing event. That didn't sound right to me, since you could just as easily describe the assassin who murdered President Garfield in 1881 as a loser or angry little nut, yet the nation endured that trauma with none of the consequences attributed to the murder of Kennedy. I leave the killers of Lincoln and McKinley out of the discussion since they could more accurately be described as terrorists in the interests of the Confederacy and anarchy respectively. Then it struck me that the whole exercise was both futile and unjustly flattering to Americans. Does any other nation have a "loss of innocence" narrative? Any nation born from revolution arguably is entitled to one, to the extent that it defines itself in idealistic terms doomed to be betrayed. On the other hand, nations born from revolution can hardly claim to be innocent because they are, by definition, born by violence. Of course, many Americans, mostly belonging to the political left or self-conscious minorities, will tell you that the U.S. was never innocent, and I see no reason to fight with them over that point. I still think, however, that "loss of innocence" is used to describe, however awkwardly, an actual epochal event in national history, even if people disagree over what specific event it was. What people have been trying to describe since the Seventies is probably better described as a loss of complacency, after which certain things once taken for granted, or ignored, can't be anymore. The Ken Burns Vietnam miniseries that played PBS last month makes (it really reiterates) a strong case for that war and the backlash against it on the home front, as the crucial moments. As "innocence" or "complacency" arguably was a privilege of white Americans, so the disillusioning, demoralizing moment came in two parts: first the spectacle of white youth protesting against their government, in apparent betrayal of the troops on the battlefield, and then the killing of white youth by the government at Kent State. It was sadly quaint -- I DVR'd the series and am still working my way through it -- to see, after watching the news from Vegas, how the deaths of only four people in 1970 traumatized the nation. And it was simply sad to see that some of the wounds of that era are still open, or barely scabbed over, even if the controversy over the proper attitude during the national anthem is just a trivial echo of the more intense controversies of half a century ago. The protests of those who feel that their nation's ideals have been betrayed, or were lies all along, still look like betrayal itself to much of the country. It should be recalled, however, that not even the Weather Underground adopted a strategy of mass murder of random victims in those days. The "loss of innocence" that accounts for the amoklaufs of our time will most likely be found closer to our time than to the Sixties or Seventies. Whether or not the search is worthwhile, at least it fills air time until someone learns something about why the Vegas killer did what he did.