There is no limit to the amount of money that can be brought out of the United States. However, if the amount is more than $10,000, U.S. Customs and Border Protection requires the traveler to fill out a "Report of International Transportation of Currency and Monetary Instruments."
According to the official website of the Department of Homeland Security, the U.S. Customs and Border Protection agency is one of the largest law enforcement agencies in the world. It patrols the borders and engages in anti-terrorism activities, as well as attending to customs, immigration and facilitation of international trade. The agents are responsible for enforcing hundreds of U.S. laws.