As far as I'm aware that cultural practice is only widespread within parts of the world where there are an awful lot of Muslims and Muslim influence. Egypt and Malaysia, for example, over 90% of the population of women is subjected to it. In Nigeria, which is only 50% Muslim, somewhere between 25% -50% of the women are subjected to it. In Somalia its 98% and in Malaysia 93%, in Mali 89%. All of the countries with high numbers of FGM are, as far as I'm aware, Muslim or mainly Muslim. The west african countries you talk about, ie, Senegal, Gambia, Mali, Burkino Faso, Guinea, are mainly Muslim. The practices is becoming popular in Indonesia, too, where, according to an article I read the authorities have given up trying to stamp it out in the face of opposition by religious authorities.