20 years ago, the world was shocked by images of two planes flying into the Twin Towers in New York. America was injured, but its response would go on to inflict worse wounds on the country’s image and influence, culminating with the humiliating retreat from Afghanistan. That was just the latest chapter in a series of damaging moral crusades, attempting (and failing) to get other countries to conform to America’s values. As a result, America has lost the pre-eminence it once enjoyed, and needs to learn to accept the world as it is, writes Michael Pembroke.