I was taught that the U.S. began as a Christian Democracy too. However:

 The problem is NOT that the U.S. was founded as a Christian Democracy. The problem now is that "Freedom of Religion" is upsetting some Christians because the Freedom of Religion is also the freedom of having no religion at all. And for many white people especially in the Heartland who have never traveled to other countries, atheists, Agnostics and other religions are too terrifying to contemplate. 

So, what I'm saying here is that there were also people like this in the 1950s too. But, most people in the U.S. have changed a whole lot from then. But, some of the more provincial people who never travel outside of their area or state and never to another country have not changed in some areas of the country and this is now a problem because of their intolerance of anyone different than them.

So, ethnocentric provincial heartland Christian thinking could very well end the U.S. democracy just like it almost ended the U.S. democracy during the Civil War in the 1860s too.

So, the problem has become a certain kind of Christian Ethnocentrism in the heartland of our country.

However, you also should know that there is also Russian ethnocentrism and Chinese ethnocentrism too. And the collision of all these types of ethnocentrism could theoretically turn earth into an asteroid belt during the next few hundred years.

And Global Climate changes are likely to anger all these groups even more than they are now and this is more likely to happen every day global climate changes get worse from now on.