Well, if Byzantium falls to the Ummayads, that is possible. let's say, in the Early 700s, Constantinople Falls, followed by Greece and Bulgaria, perhaps around the 720s so Hispania still falls as OTL...
Have them then Expand Northwards, if the Carpathian Basin is Muslim before the Magyars Arrive, then you have left Christianity with only one way east, and that is Scandinavia-Baltic-Russia, you would also have Germany and Poland, vulnerable to Raids, and perhaps even Italy south of the Rubicon might fall before the collapse of the Ummayads... you could also have the Khazars fall, or at least retreat into the Daguestan and the North Caucasus.
that however won't help the Ummayads, so there's an ATL Abbassid Empire, much more decentralized.
now, Unless Scandinavia and/or Poland go Christian, then Russia won't, no Constantinople after all, if you can get the steppe peoples like the Magyars, or the Cumans, to turn Islamic, then you have just augmented their Cavalry, so now Christianity is encircled (the Rus' might or might not turn Muslim).
Now, with the balkanization of the Alt-Abbassid, we will assume the Seljuk (or other Turks) arrive roughly OTL (a big IF) they might form a ''Caliphate of Rum'' based on Constantinople, or with some luck, in Rome Itself, however, eventually, with Islam divided, there will be some attempt at a Reconquista in Iberia and Italy.
Most of OTL India ending up more permanently muslim is also possible, but to expand further east, they will have to sort either, the Deserts, or the Himalayas, and further North and West into Europe, is unlikely (depending on whether the Poles go Christian or Muslim) if the Norse abandon their old faith it is more likely that they will go with Christianity, and I believe the same is true for the Poles... then, if the Magyars come around as IOTL and settle the Carpathian Basin, you better hope they turn muslim
now, Francia, Germania, and Britannia, are out of the question, too much resistance from the local nobles, and even if parts of them can be conquered, it won't be for too long before Christian Rule is resumed.
So, in my opinion, by 1100s, the best case is something like this for Islam
where Green is all land ruled by Islam (not necessairly with a Muslim majority) and Red, is the Christian World