it is more accurate to talk about a failed attempt by brown romans to colonize white europe that went on for thousands of years and ultimately failed than it is to talk about "christian europe". we universally condemn the inquisition, but fail to stop for a minute and realize that there were still enough pagans in europe at the dawn of the enlightenment to justify a crusade in the form of a witch hunt against them. the church was still launching crusades against white pagans in northern europe in the 17th century. it's christmas; you are still worshiping odin and not christ and should realize it. what do reindeers and christmas trees have to do with a barn in israel, where it almost never snows? that's north germanic pagan iconography. the romans spent centuries trying to pacify white tribes in the north and were eventually first thrown out of europe in the 4th and 5th century by pagan indigenous groups (the roman sources call it the great barbarian conspiracy; it was an indigenous uprising), in a process that repeated over and over again in waves of pagan revolutions, culminating in the last viking invasions. england itself, the alpha culture of north america, is based on a pagan law code that was introduced to the island by saxon pagans, who were still in power in england in the 11th century, when a warlord from france named william invaded it under the direction of the pope in order to re-implement christian rule. we gloss over the fact that the norman invasion of england was basically a crusade against the furthest fringes of roman/christian colonial rule, and against an island that refused to christianize. the brutal despotism that followed was the last serious attempt to enforce christianity on england, and it failed to even establish a christian legal code, as the saxons would not let go of their democratic institutions, but instead enforced a magna carta on the norman nobility that ultimately returned power to parliament, that constructed the common law and, within a few centuries, had thrown the romans out for good. the english kings were so unchristian by the late dark ages that they didn't even believe in monogamy, and figured a serial philanderer could run an english church just as well as the fucking pope.
but if there was any christianity in europe at all it was restricted to the nobility. the regular people of northern europe were never christians and spent centuries evading taxation from the christian aristocracies and fighting their feudalism, while returning to their indigenous belief systems whenever they could and suffering immense persecution and cultural destruction for it. they actually teach you in school that indigenous european cultures were illiterate and had no history, which any cursory investigation into the matter will expose as a brutal lie, but these histories were destroyed by the christian aristocracies in a process that did not significantly differ from what they did to the aztecs centuries later.
it is the fact that white europe emerged from this process of cultural destruction both uncolonized and as a cultural tabula rasa, with no history of it's own, that allowed it to make such a clean break from the past, when it did. europe had no choice but to start from scratch, because everything it used to have was taken from it by brown christians from rome and lost in ruins and engulfed in flames. europe wouldn't be what it is today if it hadn't been thoroughly destroyed by christianity, while simultaneously refusing to accept it. all the christians had to show for their efforts in the end was a pile of rubble and a population no more willing to accept it than it had been in the first place.
the result is that while white europeans won - we defeated christian colonization - the victory was deeply pyrrhic. we lost who we were in the process, and had to redefine ourselves by reading greek mythology, but we did it, we dd the homework, and we emerged as a new society with new institutions that had little to no cultural baggage tied to the past.
there are few constants through history, but one is that white people make shitty slaves. we can't be broken, and they've tried, over and over. we don't want your religion, we don't want your slavery. we'll burn your cities down, in the end, if you won't fuck off and let us live in freedom.
it follows that there is really no likelihood that muslims are going to succeed in taking control of this power vacuum left open by the forced retreat of christian colonialism, and if they try to do so, the same thing will happen. the danger is not in the uncertainty of the eventual outcome, but in enduring the hardship of struggling against a new type of middle eastern colonialism. it's a shitty way to spend the next thousand years.
europe will win in the end, but it may have to do so the hard way, and may have to endure a new dark age, if it doesn't learn from it's own history, and allows these middle eastern groups to try to walk into this vacuum and continue to try to colonize it. it's up to them how they want to do this.
it should be clear that white europeans will not, in the end, accept middle eastern religion. it spent a thousand years defeating christian colonialism and won, and it will spend the next thousand years defeating islamic colonization, if it must.