I don't believe in American Exceptionalism.
It's not a doctrine or even a phrase that finds wide mainstream use anymore, having mostly fallen out of favor in the 1960s. But it could definitely be argued to be a thread in the fabric of our culture and is obviously apparent in the foreign policies of our government.
I don't buy it.
What I do believe in though is human exceptionalism.
Not in any religious sense or the sense of a human right to dominate nature, but rather in the sense that humans are the primary actors on the world stage, and as such have the ultimate responsibility for our own fate.
In spite of the political and media controversy over anthropogenic global warming (AGW), there is a broad consensus (roughly 97-98%) among climate scientists that average temperatures have risen significantly over the past several decades and that the cause is manmade carbon emissions.
This is where we come in. An interesting correlation has been shown between brain size and intelligence. Perhaps more specifically, brain mass in comparison to the size of the body is a good indicator of the intelligence of a species. Compared with birds and reptiles, and nearly every other species on earth (except dolphins), humans have the largest brains and most intelligence. 
But isn't our intelligence what got us into this mess in the first place?
The odds seem to be against us. Intelligence - our ideas and innovations - created capitalism and industrialism and the ecological catastrophes Earth is now suffering. Maybe our intelligence will be the death of us.
But if we're to have any hope at all for the survival of our species, we have to believe in our own exceptionalism, in our abilities to innovate and cooperate to find a new way. Maybe humanity's defining trait, the thing that makes us most different from all the other animal species on the planet isn't our intelligence at all. Maybe what makes us most human is our ability to seemingly do the impossible. Maybe what makes us most human is our knack for doing superhuman things.
 Carl Sagan, The Dragons of Eden, Random House, 1977, 33-40.