In France, since 1905, we have a strong secularism (french secularism). Step by step people lost faith. But since twenty years, there is a revival, especially worn by the Muslim community. The new fashionable term is spirituality, not really faith but believe in some spirit, theism or pantheism. French people reject mainly the Church as an institution not religion
Those strongly religious people are mostly in the South and Midwest. Anything along the coasts is less religious too.