The structure of the essay would depend on the specific topic of your essay. Increased discussions of nationalism by writers should make it relatively easy to find useful information for your essay, regardless of the thesis. One option for a thesis would be answering the question "What is Nationalism?" If this is your topic, then you could follow the basic structure created by Umberto Eco in his essay "Ur-Fascism." Essentially, you could write an article about "Ur-Nationalism."

A second option would be to look at how nationalism has been combined with other political movements over time. Nationalism has been a component of fascist, populist, capitalist, and socialist movements at various times in different countries. Examining how nationalism became a component of each could be interesting. If this were your essay topic, then you would need to clearly structure your essay in a way that eases understanding. Your first section could be a discussion of what nationalism is or, at least, how you will be defining nationalism for the purposes of your essay. This is essential to making sure that anyone critiquing your essay is working from the same baseline.

After this initial section, you could move on to a discussion of each movement in turn, so you would have a fascism section, a populism section, and so on. Within each of these sections, you'll also need to define how you will be using the terms "fascism" or "populism," for example. Then, you could move on to discussing the movements and what part nationalism played in each. You could then end your essay by laying out some common themes between the various movements that may be important in explaining how nationalism became a component.