Hurricane Katrina matters despite the "promise and possibility of America" because it shows that the promise and possibilities are not open to everyone, particularly non-white Americans.
The book Zeitoun documents the discrimination, racism and prejudice Muslim men and women face in most parts of America, particularly after the Sept. 11 terrorist attacks. The entire first parts of the book are focused on the lengths Abdulrahman Zeitoun had to undertake to ensure his business in New Orleans would not be hurt by negative stereotypes of Muslim men in America. In a chapter that describes how a customer complained about the Latino painters who work for Zeitoun, the narrator goes on to describe how "every so often, would-be clients could not get past Zeitoun's last name." While these incidents didn't happen too often, they were "not rare enough."
These types of incidents raise a glass ceiling (a term usually reserved for women in the workforce, but applicable here) on immigrants like Zeitoun that attempt to make themselves successes in the country that has such promise and possibility.
The incidents that occur after the hurricane, when Zeitoun and his friends are arrested are even more evident of this glass ceiling that is raised on immigrants and those who do not fit in the traditional white American stereotype. When Zeitoun was being ushered through the bus station, a guard tells him, "You guys are terrorists. You're Taliban."
The entire book focuses on the effects of this glass ceiling on certain segments of society. Zeitoun is imprisoned indefinitely and gets sick.
Symbolically, Hurricane Katrina conjures up images of people of color standing on rooftops holding up signs that say "Help!" It shows areas made up of mostly African Americans completely flooded and their homes destroyed. Katrina calls to mind tens of thousands of people, who could not, or did not, leave New Orleans, starving and dehydrating in the Superdome. All of these images contradict the idea of the "promise and possibility of America." How could a country that cannot or does not take care of its own people promise possibility?
After the publication of the book, Zeitoun suffered from illness and post-traumatic stress disorder and became abusive toward his wife and radicalized. His story, which was one of immigrant success, became one of tragedy and symbolic of the false promise of America.