Disagree - yes you can have an atheist nation (China), yes you can have an Islamic nation (Pakistan, Iran, among many others), but you cannot have a Christian nation, because Christianity is the way of freedom and cannot be legislated politically.
One can found a nation on Christian principles. One of these principles is that the state owes its authority to God, not to the collective will of the people. For that collective will, uninstructed, inevitably will be enslaved by sin, and submit to the will of the few and powerful.