Often Mr. Trump’s new tariffs are layered on top of existing ones. In this case, the T-shirts were subject to a base tariff of 32 percent based on the value of the import. Many goods typically have a very low base tariff, but garments and other textile goods are subject to some of the highest tariffs.

Long-threatened tariffs from U.S. President Donald Trump have plunged the country into trade wars abroad — all while on-again, off-again new levies continue to escalate uncertainty. Trump launched a trade war during his first term as well,

The White House has said its agreements with the U.K. and China are starting points, but so far the Trump administration has given up more than it has gained.