DBWI: Later/reduced presence of Islam in the Sudan?

Say if we butterfly the Songhai jihads, and Islam spreads less south of the Sahel what are the effects on the region and the greater world?

Assuming this area remains the main source of slaves for the European empires, would the lack of Islam and limited knowledge of Arabic reduce unity among Sudani peoples in the new world? With 1 in 2 slaves in the English and Spanish practicing Muslims on arrival OTL it was virtually impossible for colonial authorities to stamp out 'undesirable' religious characteristics and at least one study has suggested they even spread, as a method of resistance to foreign rule, with the consequences we all know. Would slave populations be converted to Christianity in this timeline and would the populace be less rebellious?
It is possible. The Songhai were very unstable. The holy war to bring Islam to the pagans as far as the Congo Basin with war or missionaries is what kept the state united for a longer period.

It wasn't long until the Europeans took control over Africa. But ruling over Muslims made conversion to Christianity unlikely. Today, non oriental Christians form 17% of the African population (the oriental Christians form 7%). That is barely a quarter. If you do not count the 2% Europeans of the Cape and 3% mixed race then you end up with less than a fifth of Native Africans. Very low. Considering the success of conversion among the Pagans, Christianity could take root in Africa up to 50% had the Songhai jihad failed.

Considering slave trade... the Muslim slaves were largely captives of the Pagan Africans who were in remote areas. Due to the Muslim Africans keeping in touch with North Africa, a lot of them knew how to read and write and knew how to use weapons the Europeans had. The example is in the Abu Abbas Rebellion in the Carolinas, the largest known slave rebellion in North American history. The leader was a son of an Egyptian Arab officer and a Sudani mother. He was captured and sold as a slave. Too bad for the Slaveowners he was skilled with military tactics. The knowledge on European weapons and the Islamic identity made them a threating group.

Conversion of slaves did not work too good as the slaves kept practicing Islam in secret. Hence why the Spanish used to pressure slaves to marry Iberians or Mestizos to assimilate them by marriage. Most mixed race of African origin are Christians even today. The Anglo-Saxons did not use this until the mid 19th century to counter the one third Sudani population who were largely Islamic.
Did you know the issue of Muslims selling Muslims as slaves was so big that the Ulema pressured Muslim rulers to halt this. The King of Morocco, the governor of Egypt and the Ottoman Sultan spent together 1,000,000 Dinar over 10 years, every day since 1715, to free Muslim slaves. Slave trade was forced to end by Muslim authorities in 1795 as freeing them was expensive and it freed barely a tenth of the captured slaves.
Wasn't the dinars the Ottomans spend on emancipation the world's first sound fiat money (in terms of design, it's definitely head and shoulders above its European contemporaries)?
Wasn't the dinars the Ottomans spend on emancipation the world's first sound fiat money (in terms of design, it's definitely head and shoulders above its European contemporaries)?
I feel you're overestimating the effectiveness of the Ottoman state banking system in the early eighteenth century. Though during it's lengthy Golden age the Porte would go on to finance all sides during the many European wars backed only by the booming economy, at this point in time economic activity in the region was firmly based in silver.

It would take Chinese civil war and the resulting European silver glut to allow the comparitively stable 'carpet Dinar' (so called for it's intricate Persianate pattern design to deter forgery) realise its potential.

The emancipation program, pet project of benevolent absolutist Selim III was initially successful, leading to the abolition of slavery throughout the protestant Kingdom of France, but for the staunchly Catholic colonials, it was one of the many factors leading to rebellion and independence, greatly weakening the greatest ally of the house of Osman.
A knock-on effect would have been a probable absence of Muslim Maroon populations and the limited Islamic proselytization that happened among some Amerindian tribes in close contact with runaways and maroons.