Commentary Tomorrow, America will commemorate the 20th anniversary of the deadliest terrorist attack in human history, on Sept. 11, 2001. The annual 9/11 remembrance at the Manhattan site of the former World Trade Center towers, targets of the first and most lethal of the four suicide-airplane attacks that day that killed 2,977 people, mostly civilians, has normally been a solemn celebration of American resilience. This milestone year, however, maybe not so much. The mood of America is gloomy right now, darkened by an inflation-plagued economy, unexpected upsurges in COVID-19, an unprecedented urban homicide wave, the devastations of Hurricane Ida and the Lake Tahoe wildfire—and, most of all, President Joe Biden’s still-ongoing fiasco in Afghanistan. Withdrawing the last U.S. troops from Afghanistan, a move supported by the majority of Americans, was supposed to be a triumphant capstone of Biden’s first year in office. His administration had carefully timed the completion of …