The social media post by President Trump made it sound straightforward. The United States would orchestrate a deal to end the war with Iran and, in exchange, a slew of countries across the Middle East and South Asia would join an agreement, called the Abraham Accords, establishing relations with Israel. In fact, he said, that “should be mandatory.” But half of the countries he named — such as Egypt, Jordan and Turkey — already have relations with Israel. And the other half — including Saudi Arabia, Qatar and Pakistan — have no interest in establishing them anytime soon. As a...