U.S. Secretary of State Rex Tillerson recently said what many analysts have long been thinking: The relationship between Turkey and the United States has reached a "crisis point." The two countries' strategic partnership has been increasingly rocky as Washington and Ankara take diverging approaches to the Syrian civil war. But more than protracted policy disagreements, the decline in U.S.-Turkish relations owes to a fundamental loss of trust. Visits by key U.S. government personnel -- including Tillerson and national security adviser H.R. McMaster just this month -- have only papered over the widening rift. Although officials on both sides reaffirm the alliance's value at every public opportunity, the challenges facing the two countries may now be too great to overcome....