Link: http://www.fas.org/sgp/crs/row/R41959.pdf

From the Congressional Research Service via FAS-

"The United States often looks to Europe as its partner of choice in addressing important global challenges. Given the extent of the transatlantic relationship, congressional foreign policy activities and interests frequently involve Europe. The relationship between the United States and the European Union (EU) has become increasingly significant in recent years, and it is likely to grow even more important. In this context, Members of Congress often have an interest in understanding the complexities of EU policy making, assessing the compatibility and effectiveness of U.S. and EU policy approaches, or exploring the long-term implications of changing transatlantic dynamics."