The U.S. just challenged one of the WTO’s most fundamental rules — and it changes everything for Chinese B2B exporters. On March 24, 2026, the Trump administration formally urged WTO members to rethink the “Most Favoured Nation” tariff principle, pushing for a new system that would allow the U.S. to legally charge different tariff rates to different countries. Combined with fresh Section 301 trade probes targeting 16 economies, the window to enter the U.S. market is narrowing. Here’s what it means, and what smart exporters are doing right now.