The United States and European Union face many of the same challenges today: they must maintain economic growth in the face of global competition, harness and manage rapid technological change, and respond to diverse security threats. Yet a transatlantic partnership that has endured since the end of World War II now appears increasingly divided over how to respond. The 2016 Brexit referendum and the US presidential election resulted in victories for populist campaigns that questioned the core values and institutions created by the transatlantic powers. More recent elections in Europe have bolstered centrist candidates and helped to rejuvenate the European Union. But on questions of trade, security, climate change, and relations with Russia, Europe’s leaders have frequently been at odds with the Trump administration. On these and other critical issues, an opportunity and impetus has arisen for the European Union to assume a global leadership role that many feel the US is abandoning. Are the European Union and United States on divergent paths? How are changing geopolitical and economic realities transforming the transatlantic partnership? And how committed are Europe and America to defending the global institutions and rules they created? The Chicago Council on Global Affairs and Chatham House will convene policy experts, journalists, and practitioners for a half-day symposium to chart these trends and consider their implications.