Countries with Christianity as their state religion are in blue.
A Christian state is a country that recognizes a form of Christianity as its official religion and often has a state church, which is a Christian denomination that supports the government and is supported by the government. Though many Christian states have turned secular and adopted the separation of Church and state, church organizations still have much influence in the institutions of these nations, include hospitals and schools with government funding.
The only Christian nation in the world today is the one gathered "from every tribe and language and people and nation"... ~ Michael Horton
The only Christian nation in the world today is the one gathered “from every tribe and language and people and nation” (Rev. 5:9) to be addressed by its king. In his Great Commission, Jesus gave authority to the church to make disciples, not citizens; to proclaim the gospel, not political opinions; to baptize people in the name of the Father, the Son, and the Holy Spirit, not in the name of America or a political party; and to teach everything that he delivered, not our own personal and political priorities. And he promised that his presence with us is something that the world can never take away.
Mike says we began as a Christian nation. We didn’t. Did you miss that day in homeschool Mike? If you don’t know that the Pilgrims came here to get away from the Church of England, then you don’t know literally the first thing about our country.
Mike says being a Christian nation is our tradition and it’s who we are as a people. It’s not. We’re the people who have a First Amendment which says Congress shall make no law respecting an establishment of religion. And we have an Article Six, which says no religious test shall ever be required as a qualification to any office.
So I take these people at their word when they say that they think we should be Christian nationalists. But then they have to take John Adams at his word, when he wrote, ‘The government of the United States of America is not in any sense, founded on the Christian religion.’
Encyclopedic article on Christian state on Wikipedia