The ports of Los Angeles and the adjacent Port of Long Beach will see traffic plummet in coming weeks. Whether it’s Hot Wheels or Barbies or pretty much anything else that’s supposed to come from China to the United States, it’s mostly all getting here one way.

WASHINGTON—President Trump and his advisers have laid out several, sometimes contradictory goals for his tariffs: increasing federal revenue, strengthening the U.S. hand in trade talks and reshoring manufacturing jobs.