After 25 years, the legacy of the September 11 terror attacks continues to shape America's politics and its place in the world. A quarter-century on, what lingers in the mind from that world-upending day? September 11, 2001. Or 9/11, as it quickly came to be labelled, a term previously known as the primary emergency number in North America but now forever associated with an Islamist terrorist attack that killed 2,977 people from more than 100 countries, not including the 19 hijackers. Perhaps, initially, it was sheer confusion, as news channels interrupted regular programming to switch to images from Lower Manhattan. The North Tower...