And why leftist elites are opposed to it . . .
"The problem that liberal elites today have with American exceptionalism is simple to sum up. Before the mid-1960s, most liberals believed in it. But then 1968 happened, and the New Left took over the academy and the intellectual leadership of the Democratic Party. The New Left was not rebelling against American conservatism, which in the mid-1960s was still nascent. It was rebelling against American liberalism, and – among much else – against its belief in the basic goodness and exceptionalness of America. American conservatism is, really, a rebellion against that rebellion, fortified by the neo-conservatives who split away from American liberalism when they realized it was being taken over by the radicals."
More here. The title to the piece is quite interesting.