Nationalism kills: a global community does exist

Paul Krugman has posted a tuit where he expresses his embarrassment at some supporters of Trump who claim that a "global community" does not exist, but the world is an arena where nations compete. This is a notion common to all nationalists, for example Catalan otherwise neo-liberal nationalists who believe in the theory of competing small nations in a free trade world due to Alesina and Spolaore. The problem is that nations also compete to set (or eliminate) the rules of international trade, instead of cooperating to set them, which is achieved by basically giving up the monopoly of sovereignty. I find useful that Krugman has taken advantage of the opportunity to go back to an old idea of his: the criticism of the abuse of the word "competitiveness" in economics, by which some mean seeking advantage in a world of zero-sum competition between nations. As Trumpians try to kill the global agreements on climate change, it is a good time to remind everybody that nationalism and related philosophies kill. In the absence of global agreements and transnational cooperative action, climate change will intensify and human civilization as we know it today will disappear. As Krugman says in his old article on "competitiveness:"
"As for fear, it takes either a very courageous or very reckless economist to say publicly that a doctrine that many, perhaps most, of the world's opinion leaders have embraced is flatly wrong. The insult is all the greater when many of those men and women think that by using the rhetoric of competitiveness they are demonstrating their sophistication about economics. This article may influence people, but it will not make many friends.
Unfortunately, those economists who have hoped to appropriate the rhetoric of competitiveness for good economic policies have instead had their own credibility appropriated on behalf of bad ideas. And somebody has to point out when the emperor's intellectual wardrobe isn't all he thinks it is.
So let's start telling the truth: competitiveness is a meaningless word when applied to national economies. And the obsession with competitiveness is both wrong and dangerous."