With Egypt as a Christian kingdom, along with the likes of Edessa, Jerusalem, and Syria, it would geographically divide the Islamosphere.
If those crusader states were to hold off the eastern Muslim assault such as from the Seljuks and others, then perhaps the next crusades could be waged against the Muslims of North Africa and Spain.
If the Christian conquests in those parts hold, you might have a lot of Andulusi and Magrebi Muslims gradually migrate across the Sahara, all the way to the Muslim kingdoms of West Africa. The northern exodites would bring with them advanced concepts in science, theology, mathamatics, architecture, and engineering. This could possibly help to tech-up some of the African states before the Age of Discovery.
With the Kingdom of Egypt in Christian hands, one could have the merchants from Venice, Genoa, Amalfi, and Pisa have access through Egyptian interior, where they could sail down the Nile to trade with the Christian Nubians and Ethiopians, as well ashave a presence in the Red Sea ports, where they could hire ships that trade with the Arabs, as well with the Hindu states of India. Before you know it, goods from China may be had through the overseas route.
With Syria, Egypt, and Jerusalem under Christian rule, the rulers of any of those countries would attempt to revive the ancient Patriachates of Antioch, Alexandria, and Jerusalem, to reduce the Popes political influence among the crusader forces. By the 1400 and 1500 hundreds, with the Reformation taking place in Europe, the ruling dynasties throughout the Levant might convert from Latin Christianity. The Egyptian Princes would become Coptics, or the rulers of Syria could convert to indigenous Syrian Orthodox, etc.