From Iran to China, President Trump's global aggression has encouraged other countries to search for new ways to pressure the U.S. economy. While many countries have acceded to the president's demands, some have found a highly effective new way to fight back. Mr. Trump's aggression has given them the opportunity to test their control over choke points, threatening the United States and the global economy. One such choke point is the Strait of Hormuz. Another was seen when Beijing responded to Trump's tariffs by rolling out a licensing system for exports of rare-earth minerals and magnets that has given China unparalleled control over the global manufacturing system.