How national unity after 9/11 turned into polarization today

It has been two decades since Sept. 11,2001 and we are still learning how the terror attacks shaped our politics, military and sense of national unity. Garrett Graff is the author of the book "The Only Plane in the Sky: An Oral History of 9/11." He also hosts a new podcast called "Long Shadow" about lingering questions after the attacks, and joins Amna Nawaz to discuss its impact.