High national self-esteem is mostly a good thing, right up to where it leads to international boorishness and bullying. Being enamored of our exceptional military might and the exceptional righteousness of our cause led to foreign adventures in Iraq and Afghanistan that have cost us dearly in both lives and treasure.
National hubris leads to a false sense of infallibility and the belief that other nations' experiences are irrelevant. Conservatives openly mock the idea that we may have something to learn from our European friends. Economic and social problems in the U.S. plague other nations as well. Ignoring their successes and failures in facing these same challenges is foolish. Exceptionalism blinds us to our faults and to potential remedies. If you cannot see a problem, you cannot solve it. If someone else has solved it, why reinvent the wheel?
Even our best friends and allies have noted our tendency toward national arrogance. Winston Churchill said, "The Americans will do the right thing, after they have exhausted all the alternatives." Like Churchill, Panderbear thinks Exceptionalism impedes the pragmatism and open-mindedness essential to efficiently and effectively address our challenges. American Exceptionalism is insulting to friends and foes alike and is contrary to the egalitarian ideals that make America truly exceptional.