Vinth, you really need to read your history. Seth is right, and the Catholic Church is NOT the European superhero you seem to think that it is.
1.) The Crusades were not meant to "push the Muslims back" from Europe, since they hadn't invaded Europe. They had taken over the Holy Land, of which most Europeans didn't give a shit; most people overlook the fact that the Muslims originated in the Holy Land, though, and therefore didn't really take it over. Once the Pope saw an opportunity to unite everyone under him, though, he took it and sent everyone running off. However, once everyone saw that they could make a name for themselves rather than the Church, everything basically turned into a free-for-all and general fuck up.
2.) Charlemagne kicked the Spanish Muslim's (I believe the were called Moors, but I'm not sure) asses centuries before the Crusades.
3.) The Byzantine Empire was what kept any expansionist Muslim hordes out of Europe, and they most definitely were NOT Catholic. Perhaps the Pope thought about them during his morning bowel movement, but that's about it.