The U.S. versus Europe. One has become, in the words of President Donald Trump’s administration, an economically dysfunctional place of violent threats and no-go streets, restricted freedoms and censored media, escalating crises over immigration and a non-growing population whose unwise political choices threaten the ruin of a once-great civilization. And then there’s Europe. True, the old continent is not without its own challenges. Its major economies are only now recovering from a lengthy downturn provoked by the transition away from Russian energy, a shortage of public investment, and Mr. Trump’s tariffs. Its countries face serious political threats from extremist opposition...