When economists celebrate the 250th anniversary of the publication of Adam Smith’s The Wealth of Nations next year, US President Donald Trump’s mercantilism will constitute an incongruous backdrop. After all, his obsession with bilateral trade balances, glorification of import tariffs, and zero-sum approach to international trade has revived - in defiance of Smith’s teachings - the worst mercantilist practices.

Economists are right to denigrate Trump’s trade policies. Other countries’ unfair trade practices are not the main reason for the US trade deficit, and targeting bi...