American exceptionalism

American exceptionalism is the belief that 
Unique nation.
The US started from the American Revolutionary War. Martin Lipset calls it the "first new nation". It developed an American set of ideas (Americanism) based on republicanism, democracy, laissez-faire (no government interference in economy), liberty, equality, individualism (importance of individual).
Unique mission.
Abraham Lincoln said in the Gettysburg address (1863), that Americans have a responsibility to make sure that the "government of the people, by the people, for the people, shall not perish from the earth."