Zakaria: How Saudi Arabia played Donald Trump

US President Donald Trump attends a meeting with leaders of the Gulf Cooperation Council at the King Abdulaziz Conference Center in Riyadh on May 21, 2017. (MANDEL NGAN/AFP/Getty Images)

(CNN)The United States has now signed up for Saudi Arabia's foreign policy — a relentless series of battles against Shiites and their allies throughout the Middle East. That will enmesh Washington in a never-ending sectarian struggle, fuel regional instability and complicate its ties with countries such as Iraq that want good relations with both sides. But most important, it will do nothing to address the direct and ongoing threat to Americans -- jihadist terrorism. I thought that Trump's foreign policy was going to put America first, not Saudi Arabia.