Christians like to believe that their religion spread around the world by people voluntarily abandoning their own cultural traditions in favor of the obvious superiority of Christianity.

Actual history shows that's not what happened.

Christianity spread around the world first at the point of a sword and then at the end of the barrel of a gun.

Starting with the Roman Empire and continuing through European colonization, Christians used military power and brutal oppression at the hands of authoritarian governments to force people around the world to adopt Christianity. Those who refused to worship Jesus were tortured and killed.

The first Thanksgiving prayers amongst the Puritans of New England were not given at a peaceful banquet. They were part of religious rituals celebrating violent massacres of indigenous villages. 

Violent Christian Nationalism is nothing new. 

The founders of the United States of America crafted the Constitution to prevent the power of religion from taking over the government, because the founders knew the history of Christian Nationalism in the colonies and in Europe was bloody and despotic.

The United States is not a Christian nation, and that's an arrangement we ought to be grateful to our secular leaders for creating and maintaining.