Since patriotism is a feeling of pride in one's country, the subject of an essay can be quite varied. One suggestion is to write what it means to the writer, and discuss how it affects his views. Another idea is to write an essay on how patriotism can be demonstrated, such as flying the flag or placing a hand over one's heart during the singing of the national anthem.
The Sierra Vista Herald demonstrates that an essay on patriotism can be subjective and written from the point of view of the writer. One can also write about how others have been viewed throughout history as patriots, and include whether the writer agrees or disagrees. Because patriotism is about one's devotion for his country, the subject of the essay can be about any country. It does not have to be focused on the country of the writer of the essay. Instead, he can compare patriotism in different countries or even during different eras.
Additionally, the writer can take a look at famous patriots and write about what made them patriotic. Since an essay is about personal opinion supported by facts, the writer can choose to either agree or disagree with the popular views, as long as the viewpoint is substantiated by the facts.