The civil war across the Middle East between the Shia and the Sunni empowers groups like ISIS and al Qaeda who claim to be the defenders of Sunni rights against Shia attack.

European countries simply do not have the ideological framework the United States has in the shape of the 'American dream' that has helped to absorb successfully wave after wave of immigration to the States, including Muslim Americans who are well integrated into American society. There is no analogous French dream or German dream.

Think of ISIS as a pathogen that preys on weak hosts in the Muslim world. In fact, there is something of a political law: The weaker a Muslim state, the stronger will be the presence of ISIS or like-minded groups.

Peter Bergen Quotes