The September 11, 2001, terrorist attacks on the United States caused nationwide hysteria over issues of national security, domestic terrorism, and civil liberties. The US government addressed these issues by passing the PATRIOT Act and launching a full-scale war against terrorism and its supporters, while citizens in many parts of the country "erected spontaneous memorials consisting of candles, flags, and posters of missing people." However, the prevailing atmosphere of grief and distress soon gave way to sentiments of nationalism, patriotism, and American heroism. While this response was reflected in many pop-culture products of the time, perhaps no format was better suited to portraying "heroism" than comic books. In fact, the regular storylines of comics like Captain America and Spider-Man were temporarily suspended and 9/11 dominated the next few issues. These issues discussed the superheroes' inability to stop the attacks and asked whether superheroes could still protect society in the twenty-first century. This trauma was revisited when Marvel comics produced the multivolume, crossover superhero storyline Civil War over a period of roughly one year between 2006 and 2007. The Civil War plot, while demonstrating similarities to events that took place around September 11, was crafted as an allegorical treatment of the American Civil War and the terrorist attacks addressing contentious post-9/11 debates over national security and civil liberties. In particular, the series critiqued the American hyper-nationalism of the time by portraying Captain America's alienation from American patriotic ideology, which had previously been his character's foundation.
Erdemandi, Max. 2013. "Marvel’s Civil War: An Allegory of September 11 in the American Civil War Framework." Traces: The UNC-Chapel Hill Journal of History 2, 213-223. http://www.academia.edu/4019352/Marvel_Comics_Civil_War_An_Allegory_of_September_11_in_an_American_Civil_War_Framework2