The Biden administration’s international tax agenda suffered a setback when Sen. Joe Manchin rejected a 15% minimum tax on multinational companies this past week, dimming prospects of turning last year’s global tax agreement into reality.

Biden administration officials had planned to use Democratic fiscal legislation to enact the U.S. piece of the deal struck last year by Treasury Secretary Janet Yellen and more than 130 other countries. They wanted quick action to set a 15% minimum tax on U.S.-based multinational companies…