If the Kingdom of Jerusalem had survived, butterflies would ensure that there would be no Ottoman Empire, much less a WWI in anything like the form we recognize.
According to the conventions of this site, a TL with KoJ and also a recognizable WWI would have to be in ASB.
And there'd a much stronger case for doing so than in many good timelines that get relegated there. In general I argue that "butterflies" can be offset by "anti-butterflies;" since the "butterfly" argument rests on events and choices that are diverted by mere chaos, one can argue that in the indescribably many timelines diverging from any POD, even an ancient one (even more so from an ancient one) one can choose to look at a timeline where the merely
chaotic variations happened to vary back toward something recognizable, so the "different sperm meet the eggs, Oxford never gets built" arguments can be circumvented.
But not so much when
systematic effects of the POD would systematically change downtime conditions. If the KoJ survives for instance, even as a small state largely isolated from Western European events, it will massively distort events in the Muslim core zone and hence Eastern Europe; as you say the Ottoman regime itself--if not simply "butterflied" away--we can choose the timelines where the Osmanli family nevertheless leads a Turkish alliance that finally conquers Constantinople, even on schedule if we like--is still going to be very different. Presumably after (or just as likely before) taking Constantinople, they or any group aspiring to claim to rule in the name of all Islam will strive to dislodge this remnant of infidel Europeanism from
their Holy Land! If they succeed as seems far most likely, no KoJ--if they fail, it becomes an irritating rock in the stream of history causing major turbulence. A different Ottoman regime therefore, with different impacts on southeast Europe (and beyond).
It's pretty hard to see how the Kingdom of Jerusalem could co-exist with anything recognizable--screw the butterflies, the systematic effects are overwhelming!
In that light, wouldn't one possible PoD by a surviving Byzantine Empire? One that is strong enough to survive but weak enough to need Jerusalem as a buffer state.
Well, that was Emperor Manuel's idea I believe. Actually all he wanted was a contingent of Western European mercenaries to take back land in Anatolia; this "crusade" pretty much horrified him and it was all he could do to get rid of them by sending them against Antioch and as many points south of there as they cared to take!
Ironically, in addition to persecuting Muslims and Jews, the Crusader realms also treated Orthodox Christians as heretics. They were able to ally with and more or less recruit even more heterodox (from a Latin point of view) local Christian sects that were not united with the Orthodox. But the Orthodox were by definition loyal to the Greek hierarchy and that made them anathema to the Latins.
So, unless we have a very different course of events even during the First Crusade (such as a prior agreement to respect Orthodox religious authority, which would undercut much of the motivation of both Rome and the various ambitious feudal-origined Latin high churchmen who came along), a strong Byzantium is going to be seen more as a problem than a solution by Latin Crusader states. And vice versa; rather than working with them, the Eastern Empire will be seeking to dislodge them!
POD post-first crusade, I assume; no Fourth Crusade can help it, and a King of Jerusalem who would prefer working with the Romans instead of the "Franks" could do.
Actually, one thing I learned about so-called Crusader Kingdoms, especially the KoJ in a class I took on the subject, was that very soon after the First Crusade, the "Franks" who stayed in the East quickly came to regard new Crusaders as much more of a problem than a solution. Whatever they brought in manpower was more than offset by the fact that first of all most of them would be going away again soon, and meanwhile their enthusiasms, ambitions, and ignorance of conditions on the ground tended to disrupt any alliances and understandings with local powers the residents Outremar had delicately and painfully evolved. They'd come barging in, upset the applecart, denounce the locals as sellouts and betrayers of true Christendom, and then (if they were lucky enough to survive the hornet's nests they tended to stir up) sail off home again, leaving those who lived there to deal with wrecked alliances with no more manpower than they'd started with.
What if Muslims weren't second-class citizens and were loyal to the crown?
That would have been nice. Nice if they hadn't massacred the Jews too.
But what, in the minds of the truly mass and grass-roots movement that was the First Crusade, was the motive of this mixed but largely peasant mob but to extirpate the infidel from the Holy Land and see the New Jerusalem cleansed of heathendom (as they saw it) rise and shine in the Glory of God, and who knows, perhaps signal the coming New Millenium of the Kingdom of God? Why set off on this hard and for many ultimately fatal journey from which they probably would never return, if not for some such dramatic outcome?
The subsequent Crusades never quite matched the First Crusade--for one thing, only the First had anything like its stunning succession of victories. I think a lot of that was shock in the Muslim world that had never looked for anything like this coming from the West. But then, just about everyone involved was amazed at the nature of the Crusade as it evolved before their eyes. No one in Western Europe expected so many commoners to drop everything and march off east; no one planned for hungry mobs learning the ways of contemporary warfare as they marched passing through their territories; Emperor Manuel as I said was pretty astonished at what he got! When this mob entered the zone of recent Muslim conquests no one there had any idea what to expect of them
either.
Later Crusades were more "organized" in the light of this disturbing experience, more under the control of their noble leadership and with more understandings among European powers-that-were about how they'd conduct themselves. This, I suspect, as much as the fact that the Muslim targets of the Crusades knew much more from rumor and experience what they were dealing with, blunted their effectiveness.
For the First Crusade to have been much different than it was--well, if the initiators got what they wanted, it wouldn't have been a Crusade at all. No one really controlled the whole process. But their effectiveness, however labeled, depended on having a whole mass of enthusiastic if ill-trained foot soldiers, and medieval enthusiasm tended to equal brutal bigotry.
Or if more people who went on the Crusades stayed there instead of returning to Europe, providing a larger population to fight any invaders.
I believe that among the commoner mass that formed the main punch of the First Crusade, most of them did stay. They saw themselves as elevated in social status, stepping into the niches of merchant and landlord that they'd vacated for themselves at bloody swordpoint--this is one reason the policy of non-cooperation with Muslims and Jews continued; the invaders had largely taken their places. Among the nobles, some stayed, some went home--a lot of the nobility of Outremer was actually developed during the Crusade, arising from men who had been nobody when they set out. But actually that was largely true of the nobility of Europe in general this generation--go back 50 years and you wouldn't find the same bands of brigands running things. This was the beginning of the Medieval era as such, and the formation of the noble houses was part of that beginning.
Anyway the Kingdom of Jerusalem and I believe its counterparts--Edessa, Antioch, Tripoli--hung on to the manpower they judged they needed and had suitable places for; if some Crusaders went home it was because their prospects looked better there to them than in the new kingdoms.
If there were no
subsequent Crusades but instead a steady trickle of ambitious immigrants, that might have been better. The later Crusades however were in response to drastic failures and reverses the existing realms suffered; those particular plagues of locusts only descended on them after they'd already blown it somehow.