President Donald Trump, in shrugging off allegations that Saudi Crown Prince Muhammad bin Salman may have been responsible for the killing of Jamal Khashoggi, described the world as a dangerous place. Gulf leaders are likely to share that perception in response to the president’s seeming unwillingness to fully take their interests into account, particularly in the wake of his announced US troop withdrawals from Syria and Afghanistan. The vacuum created by Trump risks fueling greater Gulf assertiveness, with potentially messy consequences.