In time, Christianity expanded from Europe into Asia and Africa, among other places, and was able to break out of its Western cultural confinement by repeating the process by which the church's missionary center shifted from Jerusalem to Antioch and beyond. In some important respects, however, the modern shift was unprecedented, for it was the extraordinary multiplicity of mother-tongue idioms that became the subject of Christian mission rather than the cosmopolitan values of an ascendant West. Nonetheless, mission maintained continuity with its apostolic past. In examining the modern missionary phase, however, we should highlight important signposts in the indigenous culture, especially in the local encounter with the modern West. The translation role of missionaries cast them as unwitting allies of mother-tongue speakers and as reluctant opponents of colonial domination.
He extended these historical reflections further in his 2008 Disciples of All Nations. As a professor, Sanneh taught and worked at the University of Ghana, the University of Aberdeen in Scotland, Harvard, and at Yale. He was an editor-at-large of The Christian Century, and served on the board of several other journals. According to the Yale University website, "He is an Honorary Research Professor at the School of Oriental and African Studies In the University of London, and is a life member of Clare Hall, Cambridge University. He serves on the board of Ethics and Public Policy at Harvard University, and the Birmingham Civil Rights Institute in Birmingham, Alabama." Sanneh was also a Commandeur de l'Ordre National du Lion, Senegal's highest national honor. He was a member of the Pontifical Commission of the Historical Sciences and of the Pontifical Commission on Religious Relations with Muslims. Sanneh was a naturalized United States citizen. In 2018, a new institute was created in his name, the Sanneh Institute at the University of Ghana. Sanneh suffered a stroke and died on January 6, 2019. He was supposed to present his keynote paper "Themes in Reconciliation and Harmony with Reference to Contemporary Africa" at the International Harmony Conference organized by Bishop Prof. Dr. Dennis T.W. Ng in Colombo, Sri Lanka, on 7 January 2019. It turns out to be his last paper and was read out at the conference after a moment of silence and prayer. His widow, Sandra Sanneh, is a professor of isiZulu at Yale University and their son, Kelefa Sanneh, writes about culture for The New Yorker.