The rehabilitation and universalising of nationalism

I define nationalism as government in the national interest. 

Everyone lives under a government of one kind or another. In whose interest should the government govern if not in the national interest?

Since all nations need a moral system for social cohesion, it just a matter of choosing the best available religion. 

Would Immanuel Kant himself deny the universalisability of governments acting in the national interest under universal principles designed to promote world peace through being a peaceable nation?

Since there have been Pax Romana, Pax Britannica and Pax Americana, why not Pax Islamica? 

It was after all America that dealt Christianity the mortal blow of separating the church from its state with the First Amendment, and the First Amendment was based on quran.com/2/256