Clearly, American Catholics have a big problem with endorsing everything that emanates from the Vatican, and even without the pedophile priest scandals, this caused huge losses among the faithful. Islam is even more vocal when it comes to making sure believers stick to the Koran. That said, fanaticism in any form is dangerous, and wars over religion have killed more people than you can shake a stick at.
The US has a large resident Muslim population from Middle Eastern countries, and among them are surely many who just want to live a peaceful life, etc.. But some of these people have families in Pakistan or Iran, or wherever. What happens when just such a Muslim is told relatives back home will suffer or die if he doesn't join in the Jihad against the West? This is a very real dilemma.
And danamco would do well to check out this link.
http://urbanlegends.about.com/library/bl_quran_911.htm