tl;dr: no, this is not how christianity works. the sadim-effect of the state will only corrupt or impede Christianity.

Christianity is international. A nationality is a set of rules, customs and genes of a group of people in a certain area. Applying Christian morals to a nation makes it better, because the people start to strive for the transcendent, and remove the sources of their bad behavior (sins) from their nation. As e.g. Gaetano Mosca discovered, but his research takes not into account the most ridiculous Protestant heresies. Also the non or lukewarm Christian branches of a nation will be crushed by the tides of time (see Spengler's theory of cyclical history).

 Strictly speaking we don't have nations anymore. For example Germans are scattered all around the world. You'll find them in the US, Latin America, Pacific, Australia, dark side of the moon... Also Germany itself is not mono culture anymore.
Each different kind of people bring their own set of rules, customs etc. However, we still have secular states which enforce the rules necessary for a peaceful society.

A Christian Nationalist Government would need to apply and enforce the rules found (= Rule by force). But this is not how the church works because ruling elites come and go (and with them their set of written down rules). I personally think Christian ruling elites would be better than secular ruling elites, since the former would try to improve the country instead of leeching off resources. But these elites will come by themself thru the tides of time. 
Right now Christian nationalism in the West is a pipedream and a waste of time. The broader western world enters a civilisatory winter (see Spengler). If you want Christianity around you: be the first one. repent, get baptized, received the sacraments of the church, read in the life's of saints and live your life. The salvation of your soul is more important than petty politics.