Maybe, the Christian kingdoms would realize the true threat the Musllims posed to Europe, reconcile any differences they had, and arrange a strong Christian coalition against the Moors.
The Islamic invasions were greatly aided by the weakness of the states around them. They expanded until they hit something that was strong. Easy plunder was an important motivator just as much as religious fervor. Byzantium and Persia had been weakened by their just ended war. Visigothic Spain was recently divided in civil war.
Given that Spain was at the far end of the war to the Arabs, and they were at the end of any kind of support, if Spain was united and strong at this time, it is very possible the Muslims would never had invaded. If their initial raids were defeated, the Muslims could easily decide Spain was too much a hard target, and many of the potential invaders might look for somewhere else to attack. Worst case for Europe, the Muslims might do an early invasion of Sicily and from there attack Italy. Best case, is that they disperse and if they invade anyone, it is farther east in Central Asia or India.
The best POD to avoid conquest is that the succession to the Spanish throne around this time was not contested, and the Visigoths had a strong leader.
The Muslims had only completed their conquest of the Maghreb in 709. The invasion of Spain occurred in 711. The Visigothic king Wittiza died in 710 or 711 when he was still in his twenties which lead to the division of the kingdom. If Wittiza had lived, or the succession was not contested, or if another had become king earlier and provided strong leadership, then there might not have been any opportunity for the Muslims to expand.