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.
Well, it could be about various things. It might be a story that delves into the darker aspects of the American experience, perhaps related to the struggle for success where people face hardships that seem like a nightmare. Maybe it's about someone's journey through difficult times in America, like facing poverty, discrimination or a broken social system.
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.