Parag Khanna's
"Waving Goodbye to Hegemony" is necessary reading for anyone interested in the question of the U.S. role in the world. It's like stepping out of the house and looking at it from the street. If you mostly follow U.S. news and media you have spent most of your time looking at the insides of that house and very little time at seeing how the other houses on the same street have changed. There's a new McMansion near the corner, for example.
This doesn't mean that I'd agree with Khanna on every point, but the article is a very good start for a discussion.