Raymann said:
You'd need to change the Bible for that to happen, Christians believe that you have hardship in this world, you have to turn the other cheek, and that all your rewards (unspecified) are in the after-life. Islam teaches that if you fight the good fight now, you will have your rewards in this life and the next and if you should die, well we all know about the virgins. Islam could very well be mostly a peaceful religion but it lends itself very easily to a militant side.
Actually, you wouldn't need to change the Bible. You would need to change recent history, though. Mainstream (i.e. European and, for want of a better word, Neo-European) Christianity has gone through a process of domestication and secularisation second to few others, and similar to what happened to many branches of Islam in the 10th and 11th centuries (and is happening now). After all, if you look in the right places of the NT you can find nice quotes to the tune of 'hate your father and mother' or 'sell your coat and buy a sword' (which, incidentally, indicates that either the disciples were well dressed, or military hardware was going very cheaply indeed). They just don't emphasise them any more.
If there had been a more militant strain of Christianity surviving or being restored in the Western mainstream, we might well see a Christian Al Quaeda-analogue. Given the level of fear of Islam that now exists in many western countries I am now more afraid than ever of it, in fact. People have been angry about Islamic terrorism for a long time, but in my experience people do the most ugly and indefensible things when they're afraid, not when they're angry. Of course, their attacks would be against non-Christian non-US targets, so you have to ask yourself what their version of 9-11 would have been. Mecca? Petronas Towers? The Chinese People's Assembly Building? Any group that attacked US targets would have been brought down long before they got up to anything the size of 9-11 (Al Qaeda had a long period of grace because their attacks wereon foreign soil, and, perversely, because you 'expect' that kind of thing in the Muslim world).
The reaction - shock, I'd assume. On September 11th, I remember fervently hoping that no Palestinians were involved, but I never considered that Fundamentalist Christians might be. Thus, when Al Qaeda was presented as the culprit it didn't surprise me. If a Christian group had been - I don't know. I'm not terribly pro-Christian, anyway, and I'm afraid this could have pushed me farther along. I like to think I have my emotions and thought processes fairly well separated, but to say you're not affected is illusory. Quite a few more people might have been, as well. I could even imagine anti-Fundamentalist demonstrations or pogroms in some places (there is a very Fundamentalist 'Elim' community in our city that could well have become a target). What next?
If the group responsible had been domestic, I'd envision an even tougher version of PATRIOT (though also a more controversial one as more people would feel themselves under suspicion by association) and a lengthy period of less interventionist foreign policy as America attempts to exorcise her own demons. The fallout could get nasty in the medium term, especially as it reinforces the perceived political divide between Christians and Secularists. Fortunately, most secularist politicians are unlikely to make hay out of it, but some will, and that could get ugly, too. Imagine Reopublican candidates juxtaposed with the image of the burning towers and the face of whoever is the culprit. That could drive some Christian Republicans into the same relativist camp some left-wingers now find themselves in. I woulddefinitely expect support for government policy to peter out sooner and become a lot more painful than OTL. Just remember the debates after Oklahoma City and raise to the power of ten.
An attack by a foreign group (and there are Christian groups out there who are both violent and consider America an aberration) would likely have brought very similar reactions as OTL, though with different targets. Of course, actual foreign wears areunlikely as there is, to my knowledge, no majority-Christian state at the moment that would consider sheltering terrorists after such an attack (with the possible exceptions of the Bosnian Republika Srbska, and perhaps Ossetia), and Saddam Hussein as a scapegoat is right out ("The man has a history of lies. Of course he pretends to be a Muslim, but we know for a fact that the building in the centre of Baghdad our satellite photos show is actually a church...."). Instead, I would expect a closer cooperation with secularist regimes, a great joint intelligence effort, and thus less strain on America's foreign alliances. Places like Poland, Croatia, and indeed Germany mightfind themselves eyed suspiciously as the influence of the churches is scrutinised with greater care.
Internally, there would be the same painful soul-searching, though to a lesser degree. it is hard to accept that your own faith can inspire such a thing. Some Christians will fall from their religion (some may embrace Judaism), and many will proclaim the perpetrators weren't 'real' Christians, but some will also find that the motives of the killers are understandable, though their methods must be condemned. How society deals with them would probably depend on their numbers. if it's just an odd voice in the wilderness, ostracism is the way to go. If it's a few, the whole thing could give rise to paranoia and somekind of 'purity test' for outspoken Christians (like today many people socially expect Muslims to openly distance themselves from Al Qaeda. Nobody ever asked me my position on Hitler...).
Could the fallout give greater power back to the established churches, given that the terrorists are unlikely to be mainstream Catholics, Lutherans, Episcopalians, Reformed or Orthodox? In the medium term, could it give a boost to the Democrats, Labour, and left-wing parties in Europe? I guess thatwould depend on how close to the mainstream the perpetrators were. If we're talking radical Creationist Baptists or anti-Vatican II breakaway Catholics the result might be a stronger re-secularisation. If it's Syrian or Maronite Christians, the impact will probably be quite marginal, given they're just another bunch of funny foreigners with murder in their hearts.
Either way, the Chinese government is going to do the happy hamster hop.