In a scathing essay Trump and his New Nationalist supporters, Daniel Krauthammer observes that Trump defines national “greatness” as “winning”: “That was what his whole campaign was based on. His language is never about political ideals; it is about defeating opponents, being better than the other guy—win, beat, kill, huge, rich, big league. His sense of national greatness seems largely transferred from his views of what makes a business or an individual (namely himself) great: wealth, power, status, deal-making. Greatness is achieved, most fundamentally, by winning a long streak of zero-sum competitions.”
But some of Trump's policy prescriptions make it more difficult for America to “win.” As Krauthammer says, Trump's “rhetorical focus remains on protectionism against foreign imports, immigrant labor, and corporate outsourcing—strategies that have done more harm than good for Americans' material well-being over the past century.”
Suppose, for instance, that a US firm wants to open a factory in Brazil. Brazil insists that the factory be in Brazil, manned by Brazilians. Trump would, presumably, discourage such a deal. But that doesn't mean the factory doesn't get built. And the alternative isn't that the factory gets built in the US. Instead, it gets built by someone else, perhaps by a Chinese firm. The US firm loses, and US workers lose because a factory in Brazil might need component parts made by American works in America.
If Trump's policies win, America loses. His policies will erode the greatness that he claims to be restoring. That is, if Trump really believes in America-First protectionism and if his policies actually get enacted, both of which are doubtful.