In follow-up to the chain of posts below, the following may be useful, and I speak with no small authority:
1) First, let's speak about Catholicism and Islam. The documents of the Second Vatican Council more or less equate the Catholic faith and Islam, such that official Catholic theology today states that an observant Muslim is just as righteous as an observant Catholic. My personal opinion is that the Catholic higher-ups were looking to make a quiet agreement with Islam, as if two major corporations looking to divide a market. However, Islam is now flexing its muscles, and the Catholic church is weakening. It's not outrageous to imagine a day when there's crescents on the domes at Saint Peter's in Rome.
2) As for immigration, this came back to my mind recently, and it's profound: Years ago, I was at a Catholic social function, and I overheard a conversation between a Catholic layman and an assistant to the local Catholic bishop (a midwestern city of roughly 1 million people). I can recall the bishop's assistant openly making the following statement: "The bishop really envies the Mexican bishops. I mean, they have a LOT of political power in Mexico. Nobody pays attention to the bishop here." It didn't mean too much to me at the time, but it surely explains a lot now. If you can't get the congregation to mind, then change the congregation.
et