Previous transatlantic clashes over diverse issues such as climate change, the detainees at Guantánamo Bay, and the Iraq War exposed a breakdown of mutual understanding, sometimes stemming from sharp differences over how best to achieve certain common objectives. But the wiretapping crisis and other troubling revelations from the former American intelligence contractor Edward J. Snowden point to a deeper problem: a crisis of mutual distrust that risks becoming a serious transatlantic rift at a time when closer political, economic, and security cooperation between Europe and the United States is needed more than ever.