I feel like Samuel Huntington's "clash of civilizations" idea gets thrown around all too often as a buzzword without any recognition of the dimensions of the actual argument.
Here is the original article, which Huntington later filled out to book form. It's a little long, but it's quite straightforward. I'll add just a few comments.
I think the Clash of Civilizations is one of those concepts whose success largely depends on the fact that lots and lots of people desperately want it to be true, and lots and lots of people desperately fear it is. I feel that when most people use the term, it signals more their intentions about how they want the world to turn out than their beliefs about how it is turning out. It is one of those ideational creations whose scope is so large and so totalizing that it is difficult to really come to terms with in any sort of rational and analytic way. One must accept it or reject it, because our minds can't really render partialized versions of it.
The notion itself is Romantic; in fact, one of Percy Bysshe Shelley's longer poetic works is called The Revolt of Islam. The fascination with the monolithic and the immutable is a constant Romantic preoccupation—taking things at their broadest point and shuddering at the vastness one confronts. In other words, I believe the Clash of Civilizations is as much an aesthetic idea as it is a political analysis. I don't mean to say it is definitively analytically wrong, but it is popular because it is inspiring, and unpopular because it is frightening.
This (rather hilarious) article in Slate about the lack of American interest in the Olympics captures this thirst for patriotic inspiration succinctly: "To rejoin the global sports community, we must come up with someone or something we hate as much as everyone else hates America. Until that happens, we will suffer the fate of all empires. Our victories will no longer thrill us, and we will not recognize our defeats as our own." One cannot do much more than shudder or cheer at the prospect of America finding that something to hate.