The western world is nearly destroyed by the onset of the Bubonic Plague. When the dust settles, the Muslims are poised to invade Europe, and do so. By the time of the Renaissance OTL, Europe is deeply Muslim, and the Pope has ceased having any power. By the time of Columbus, the Muslims have launched a crusade against the Orthodox of the East, driving the Christians from the Caliphate of Thenas (Greece) who settled in Malorussia and the Orthodox Empire (Russia). There was much strife between the sects of Islam in North America as they fought jihad against the infidel American Indians.