We project so much power and do so much to keep the peace that there isn't much of a need for other countries to spend on their own defenses. They don't feel threatened by anyone and go so far as to say that we are a threat by being the only super power!
Unfortunately, just like New Orleans realized how decayed and inadequate their hurricane defenses were, perhaps the Europeans will also have their morning after mourning.
It won't last forever so once it ends the Muslims will conquer Europe.