Yet today, the US continues to hold overseas territory. Besides Guam, American Samoa, the Northern Mariana Islands, Puerto Rico, the US Virgin Islands and a handful of minor outlying islands, the US maintains roughly 800 overseas military bases around the world.

None of this, however – not the large colonies, small islands, or military bases – has made much of a dent on the mainland mind. One of the truly distinctive features of the US’s empire is how persistently ignored it has been. This is, it is worth emphasising, unique. The British weren’t confused as to whether there was a British empire. They had a holiday, Empire Day, to celebrate it. France didn’t forget that Algeria was French. It is only the US that has suffered from chronic confusion about its own borders.