This article from Fareed Zakaria of Newsweek is long but an absolute must read. The article starts off by talking about the relative decline of America with respect to the rest of the world but it goes on to put things in proper context.
It's true China is booming, Russia is growing more assertive, terrorism is a threat.
But if America is losing the ability to dictate to this new world, it has not lost the
ability to lead.