Michael Totten in todays WSJ
The American superpower is an original. It's reluctant and self-doubting. Most Americans just aren't that into it. Policing the world is deadly, expensive, exhausting and thankless. France can unilaterally invade a former colony like Mali and endure nary a peep, but anti-American protests break out all over the place whenever the U.S. intervenes anywhere, even with authorization from the U.N. Security Council.
Strutting around the world like a colossus doesn't appeal to anything in the American soul. We do it because somebody has to, because we can, and because most of us sense instinctively that we'll wake up in a different world if Russia and China take over the job.
France stepped up in Mali for a similar reason. Because somebody had to, because Americans didn't feel like it, and because the French could.
Probably the best case for American Exceptionalism. We're the world's best cops because we don't want the job.