What countries use secularism in today's world?

Most countries are secular, though only the USA has a specifically secular constitution. While there are some 'officially' religious countries such as Greece and Dennmark, their values are mostly secular and the influence of the priesthood is very limited. The non-secular religious countries are mostly Islamic, in a belt running from Mauritania, along North Africa and through the Middle East to Pakistan.

Most European countries were formerly deeply religious, and have slowly become secular through dissent and critical thinking, which recognises that religion is not an equitable basis for forming law that has to apply and make sense to all, regardless of their personal beliefs. In Islamic countries where the priesthood has a strong influence over policy, this process of dissent and criticism is at best discouraged, and at worst punishable by law with death sentences.