President Barack Obama is embarking on a global swing Tuesday to encourage partners in the Gulf and Europe to scale-up the fight against ISIS.But the trip comes amidst revived attention to Saudi Arabia’s perceived role in the September 11 attacks and tensions between Washington and Riyadh over Iran, while domestic E.U. concerns distract European leaders.And then there’s America’s own domestic diversion: the acrimonious presidential race battle back home, which foreign ...