Preface: I'm neither a Crusades nor a Spanish Medieval specialist. This ended up being a lot more of a summary of the intellectual background of crusading, because I get that more, and it's a way to think about this question

So to answer this question, we have to do a little bit of historiographical background first. The First Crusade is often written about as if it sprung ex nihilo from the mind of Pope Urban II upon reading a letter from Emperor Alexios I of Byzantium, and was then preached to utterly shocked crowds who leapt up with religious fervor and cried "Deus Vult!" Then the all wandered down the holy land and conquered themselves one Jerusalem, slightly used. This narrative is somewhat misleading, which is what will will bring us, in a rather roundabout way to Spain.

The union between religion and warfare wasn't alien to the medieval world, or to Christian Theology, in the 11th century. Prayers and masses invoking divine aid in conflict, particularly with non-christian enemies, had been a longstanding part of Christian devotion. However, theologians, had sketched out a picture of what war that God could sanction would look like, and it had, at least in theory, pretty strict requirements (A just cause, a rightful authority, the goal of peace rather than gain). Violence, as a general rule, was seen as inherently sinful, though permissible in certain circumstances. The crusades, and the concept of Holy, Church Driven warfare (The church had sanctioned and supported secular warmaking, but never organized it on a large scale) developed out of a couple of main places.

The first thing we need to talk about (It isn't Spain, sorry, we'll get there), is Church Reform. The Reform movement, particularly spearheaded by Pope Gregory VII at to a slightly more moderate extent his successor , the famed Urban II (Victor III was technically in there but he was only pope for about a year vs more than a decade for the other two), had a lot of goals, and I won't go into too much detail, but generally, it aimed to morally reform Latin Christendom, purge corruption in the church, and importantly, establish much stronger papal control over the church and to some extend, lay lordship. Pope Gregory the VII, among other things, really wanted to bring the whole of Europe under some form of papal monarchy, as part of his vision for the coming days. Christian eschatological (end times) thinking had always been really concerned with the birth/death/rebirth pattern, and that's how Gregory tended to view Christian relationship with the Islamic world. Christian civilization had been born and expanded from Christ's birth to the seventh century, been driven back, and now it would be reborn more holy and crush the Muslim enemy. To this end, one of the biggest things that was done by Gregory's curates is codify the process of giving indulgences for soldiering in defense of Christendom, which was an old but fairly rare practice in the 11th century: Only the pope could do it, in line with the "Proper Authority" in Just War doctrine. To that end, Gregory and Urban both attempted to unite Christendom under papal rule to drive back the invaders, which is what finally brings us to Spain

Just before the first crusade, Medieval Spain actually formed one of the primary frontiers between the Islamic World and the Latin West. While Muslim conquests in the East were disturbing to Western Christians, they did not yet pose a serious threat to the Latin Kingdoms. Byzantium was certainly on its heels after its defeat by the Turks at Manzikert, but it was hardly beaten. Sicily and southern Italy were important, but also fairly local concerns, are arguably more important because of papal-imperial politics than because of the Muslim-Latin conflict. Sicily was far from the major Muslim power bases, (The former Caliphate of Cordoba in Spain, now broken into independent kingdoms, the Seljuk Turks in the Eastern Mediterranean and Persia, and the Fatimids in Egypt) and fairly marginal in general to the Latin West. While definitely part of Gregory's idea broader war against the Muslims, the conflict ended in total Latin victory a few years before the crusades.

Spain, however, was a bigger test of Papal power: rather than essentially one Latin faction (The Normans, in Sicily), the Spanish kingdoms were fractious, and often as likely to ally with minor Muslim powers against Christian rivals as to unite with Christians against Muslims. However, a combination of a series of ambitious Castilian Kings and papal attempts to unify Christians against Muslims really started to build up the ideology that would become crusading in later years. Papal indulgences for warriors, instructions to unify against Islam and forget old conflicts, and attempts to bring the Spanish Church in line with the Latin Rite were all part of this buildup of papal influence over the country. It got into the popes' minds, so to speak, the fact that papal influence and leadership, combined with its power to levy church taxes on kings to raise funds and to proclaim indulgences for fighting could be powerful forces to unify Christendom. So when Urban II got that letter from Alexios, Sicily and particularly Spain were probably on his mind when he decided to preach the First Crusade. Spain, one could argue, really was the 0th Crusade, so to speak. It was the Crucible in which a lot of the ideology that would set popes up to preach Crusades later on.

It's clear, from the first moment, that Urban understood the conflict in Spain to be basically part of the same thing as the First Crusade. The Crusade indulgence specifically extended to those fighting in Spain, to avoid drawing off warriors from that conflict in a rush to Jerusalem. From a canon law standpoint, Spain was just as much of a crusade as the march on Jerusalem was. However, this begins to get us into what I think the big difference is between Holy War in Spain and Crusade in the Levant. The key things that made the First Crusade so popular and influential was merging the old christian tradition of spiritual pilgrimage to the Holy Land and armed attack on a religious enemy. The big thing that got people going was the idea of an armed pilgrimage, ending in the Holiest site in Christendom. Whatever Popes' said Spain never had the same draw. Popes would continue to to propagate Crusade Bulls (Proclamations of a crusading indulgence) and try to raise funds for campaigns in Spain, but these always played second fiddle to the Campaigns for Jerusalem, and were almost exclusively the province of Spaniards and nearby Franks. Spain might have had holy sites, and the ideas for armed pilgrimages to those might have animated locals, but the war just never had the Transnational draw that campaigning in the holy land did. Hell, even in those campaigns, it was always a huge issue for Crusade leaders to do anything but drive straight for Jerusalem, even if that was militarily not an ideal solution. The average Crusader wanted to get himself to the Holy Sepulcher and fulfill his crusading oath. That was the drive, and anything that seemed to get in the way of that holy mission, even military practicality, was not popular with the rank and file.

In sum, not only was Spain, in the eyes of the Pope, a Crusade, it was a Crusade before the Crusades were Crusades (To be clear, the actual word, Crusade, doesn't pop up for a couple of centuries, so it's anachronistic to use it to describe even the First Crusade, but I think you understand what I mean). However, as important as the Spanish war was, and as much as I'm sure religious belief was a powerful motivator to warriors in that conflict, it was always second fiddle to the Holy Land. Even that extension of the Crusading Indulgence to Spain wasn't really to draw warriors there, but to keep them from abandoning their home when it was already at war. So it was a Crusade, but there's also a reason we thing about the First Crusade as a separate thing: The Crusading Fervor that swept Western Europe was always for Jerusalem, not Cordoba.

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Chevedden, Paul E. “Pope Urban II and the Ideology of the Crusades.” The Crusader World, 2015.

Chevedden, Paul E. “The Islamic View and the Christian View of the Crusades: A New Synthesis.” History, vol. 93, no. 2 (310), 2008, pp. 181–200.

Gaposchkin, M. Cecilia, editor. “The Militant Eschatology of the Liturgy and the Origins of Crusade Ideology.” Invisible Weapons, 1st ed., Cornell University Press, 2017, pp. 29–64. JSTOR, http://www.jstor.org/stable/10.7591/j.ctt1mmfs2h.8.

Madigan, Kevin. Medieval Christianity: A New History: A New History. Yale University Press, 2016.

MARIN-GUZMÁN, ROBERTO. “Crusade in Al-Andalus: The Eleventh Century Formation of The Reconquista as an Ideology.” Islamic Studies, vol. 31, no. 3, 1992, pp. 287–318. JSTOR, JSTOR, www.jstor.org/stable/20840082.

Tyerman, Christopher. “Violence and Holy War in Western Christendom.” The Routledge History of Medieval Christianity.