How did islam become part of north african cultures?

The Prophet Muhammad reminded the Muslim world, “We are a single community, distinct from others.” The distinction shapes the Muslim’s religious identity and underlines the nature of the Islamic ideal, whether the purity of the monotheistic concept, the uncompromising quest for morality, or the lifelong seeking of knowledge.  It also accentuates the common historical thread running through the international Muslim community.

In Global, African, and Near Eastern studies, the role of the African Muslim may be the most overlooked by Western academia, and involve the most tenacious myths about the spread of Islam. The lack of African sources allowed scholars to make false assumptions as they evidenced the old axiom, “scholarship follows the national flag.” The dominance of Western scholarship resulted in complete silence about African creativity, innovation, exploration, trade, and skills in scholastic writings and textbooks.

separation of church and state? not sure what you mean.