Political leaders and their lapdogs in the media and higher education speak of nationalism as if it merely consists of neo-fascist efforts to purge the world on behalf of a specific nation-state over against the other alternative of a globally unified body that governs the world.
But these nationalist movements (including Trump’s) are actually just efforts to localize political representation. The national is preferable to the international. And the local is preferable to the national. And so on such that every comparison prefers decentralization to centralization.
In other words, nationalism is smeared today and placed in the most egregious of contexts whenever it is spoken of by the global elite (Macron in France for instance). But they smear it because more nationalism means less control for them at an international level.
Nationalism is merely the idea that there is a culture, a people connected by language and customs, that is more important than giving all that up for some vague idealistic internationalist vision. Of course, the left (which has also destroyed the once conservative parties in the US), has done a great job of destroying the culture such that there no longer is much of a “nation” at a federal level— which means secession and nullification and even more localization is called for. But compared to internationalization, nationalist movements around the world (Brexit and the dissenting and agitating separatist grassroots spirit that elected Trump) are healthy and needed.
More thoughts on nationalism posted in comments.