Rush Limbaugh sums up well what American Exceptionalism really is.
The United States was considered "exceptional" because it was self-created at a time when other nations were either ruled via conquest of the strong over the weak, or were hereditary dynastic monarchies that sustained through inter-marriage between nation-states.
The United States was "exceptional" because it was the only nation created by a social compact amongst the people to live within the guidelines of a constitution and its derived laws, established by the people with the consent of the governed. Power was transferred via non-violent means, and the people adhered to that social contract.
People today don't remember (or were never taught) why the phrase "American Exceptionalism" came to be.
-PJ