President Trump says there’s an easy way for Apple Inc. to avoid his tariffs on China: make its products in the U.S. But this would be a hollow victory. If Apple follows his advice, Mr. Trump will have grabbed the least valuable link in the electronics supply chain with little net benefit to Americans, without addressing the real contest in global trade.

That contest is over the more valuable production steps like research, design and the manufacture of more sophisticated components where the U.S. is dominant but China is...