It was “the day that changed everything,” until it didn’t. Even in the immediate aftermath, you could see that 9/11 was less momentous for some ­Americans who were at a safe remove from the carnage and grief. By late September, the ratings at CNN, then 24/7 terror central, had fallen by more than 70 percent. As I traveled across the country that grim fall to fulfill a spectacularly ill-timed book tour, I discovered that the farther west I got, the more my audiences questioned me as though I were a refugee from some flickering evening-news hot spot as distant and exotic as Beirut. When I described the scent of burning flesh wafting through Manhattan, or my ­sister-in-law’s evacuation by the National Guard from her ash-filled apartment on John Street, I was greeted with polite yet unmistakable expressions of disbelief. #Sept11