The letters listed a range of tariffs. Goods entering the U.S. from Japan, South Korea, Malaysia, Kazakhstan, and Tunisia will be subject to a 25 percent levy. There will be a 30 percent levy on South African and Bosnian goods, while imports from Indonesia will be subject to a 32 percent rate.

A small company in northern Mexico had faced steep competition from China in making straps, plugs, fasteners, grommets, zip ties and clamps. Now, U.S. tariffs have driven a spike in his business.