The first concept of American exceptionalism was religious; after all, we still quote, somewhat out of context, the famous Puritan statement about the shining city on the hill. It didn’t last. Most of the colonists that followed were more interested in improving their material lives than in religious practices, particularly since Great Britain accepted a degree of toleration in the late 17th century.
The second version of exceptionalism came after the Revolution. The new nation, unlike the European powers, was a republic, and was mostly disengaged from European power politics. Partly due to geography, partly due to its weakness, and partly from principle, America did its best to focus on its own development and ignore the rest of the world. It did not evangelize for anything.
The 19th century version of exceptionalism revolved around economic opportunity and the frontier. America was the place to which immigrants came to make a better life for themselves. The rate of economic and population growth and technological change is what made America special in the eyes of its citizens and the rest of the world.
The first glimmerings of the notion that America’s liberal democratic system should be universally emulated came from Woodrow Wilson. Wilson’s attempt to remake international politics failed, however, and the nation returned to its historical indifference to the world until the thirties. It was FDR and World War II that changed America’s view of itself and the world for good. Henceforth, America would do its best to midwife liberal democracies around the globe, because its own liberal democracy, it was felt, could not survive in isolation against fascists and communists.
During the Cold War, American leaders had to do business with innumerable right-wing thugs in the name of “democracy,” by which we really meant opposition to communism and Soviet influence. After the fall of the USSR, we briefly had the opportunity to pursue the Wilsonian dream of universal liberal democracy without resorting to Cold War hypocrisy. That dream died in Iraq, however, and a rising China means dealing with some unsavory characters in order to counter, well, Chinese exceptionalism. We are in effect back to where we were during the Cold War–still offering American liberal democracy as a universal political concept, but only pushing it when it is consistent with our interests.