Leftism and Islamism are the two main threats we face. (Sorry, Al, your global warming is about as much a threat to us as your marital cooling.) Both threats are totalitarian and the threat is 'synergistic' inasmuch as leftists tolerate and enable militant Islam, which is obviously inimical to their modus vivendi, all the while displaying the most vicious intolerance of Christianity which is little or no threat to them. I develop this theme in What Explains the Hard Left's Toleration of Militant Islam?
To help you think clearly about these important matters, I recommend Dissecting Leftism and Jihad Watch.