I don't think 'American Nightmare' is a true story. Usually, works with such names are fictional works of imagination, crafted to engage and thrill the audience through fictional scenarios and characters.
Well, generally it is. It delves into various aspects of what can be considered an 'American nightmare' like poverty, social inequality, and the struggles of the underprivileged. It compiles real - life stories and data to present a picture of the not - so - rosy side of the American dream. For example, it might show how certain communities are left behind in terms of education and economic opportunities, and these are real issues that people are facing in America.
In fact, 'American Nightmare' is purely fictional. It was crafted by the imagination of the creators rather than being inspired by actual happenings. The story and its elements were made up to entertain and engage the audience.