No, you do not typically go through "customs" when leaving Europe; you go through Passport Control (Immigration) and potentially a security screening. Customs is the process of declaring goods you are bringing into a country. When you exit the Schengen Area (most of mainland Europe) or the UK to return to the U.S., an immigration officer will stamp your passport or scan your biometrics to record your exit and ensure you haven't overstayed your visa-free period. However, the actual customs process happens upon your arrival in the United States. Once you land on U.S. soil, you will collect your bags and pass through U.S. Customs and Border Protection to declare any items you purchased abroad. The only exception is if you are departing from an airport with U.S. Preclearance (like Dublin or Shannon in Ireland), where you would clear both U.S. Immigration and U.S. Customs while still on European soil before your flight takes off.