As Trump revives tariffs as a weapon, the European Union counters with long-term economic strategy, finalizing a massive Mercosur trade deal that weakens U.S. leverage, reshapes global supply chains, and proves competence beats confrontation.

As Trump revived his familiar playbook—floating a 10% tariff here, threatening 25% tariffs there—he framed the move as strength. A warning shot. A reminder of American...