José Manuel Barroso, the former prime minister of Portugal and former head of the European Commission, used to say that Europeans were in love with “the intellectual glamour of pessimism”. When I first heard him say that in 2005, I had just started as a correspondent in Brussels after a few years living in the US, and his words rang especially true. There was a stark contrast between the deeply rooted American cultural belief that things could only get better, and the routinely bleak view that prevailed in many European countries, even the wealthiest and most privileged ones. France, Belgium,...