The idea seems related to start-up culture as well (think "two guys in a garage", and "we're different" as well as "war stories from back in the day" during shareholder meetings).
Time will tell if setting ourselves apart sets us up for failure in the long-term.
Maybe 'global superpower' wasn't a metric early America used to inform its (yet unnamed) notion of exceptionalism. Your quote from Jefferson speaks of an "empire of liberty."
This could make sense if you think about it. Young America had just accomplished the almost unthinkable feat of winning independence from the Globe's biggest superpower of the time. In winning this liberty, the young nation began its life by defining itself through this hard won liberty.
In a sense, America's view of what made it special might have been a response to and departure from the concept of a superpower (which it had just cast off).
The characteristics he lists:
>monument of human rights...freedom and self-government...it is to be lighted up in other regions of the earth if other regions of the earth shall ever become susceptible of its benign influence.
His dialogue doesn't involve power or might, but rather rights and example. Even the hopeful spread of America's influence is framed as something to be willingly adopted and benign.
I'm not a student of American history, so I don't know how consistent this interpretation is with the other writings and beliefs of the day, but it's really sad to me how far we've fallen from this ideal. The modern American practitioners of American Exceptionalism seem to have perverted it beyond recognition. Especially when you look at how many of these same administrations prop up dictators when it serves our perceived interests.
From wikipedia:
Jefferson envisaged America becoming the world's great "empire of liberty"--that is, the model for democracy and republicanism. He identified his nation as a beacon to the world, for, he said on departing the presidency in 1809, America was:
"Trusted with the destinies of this solitary republic of the world, the only monument of human rights, and the sole depository of the sacred fire of freedom and self-government, from hence it is to be lighted up in other regions of the earth, if other regions of the earth shall ever become susceptible of its benign influence."[37]
Off-topic: that wp [1] page states that american decline started at the end of the eighties. It makes an interesting read as I think the mass media put it around 9/11. Happened before 9/11 but that event crystallized that decline.
[1] http://en.wikipedia.org/wiki/American_exceptionalism
Edit:
1. The US declared independence in 1776 and were recognized in 1783. Is 30 years between this and Jefferson statement too much to say "it was there from the beginning ?"
2. What about 1600's and 1700's US religious people and their own beliefs when they established themselves in that new promised land ? How does it relate to "American ideology, "Americanism", based on liberty, egalitarianism, individualism, republicanism, populism and laissez-faire." (from the first paragraph of that wp page) ?