In 2002–2003, he joined the White House staff and served as Director of Andean Affairs advising the President and National Security Advisor on issues pertaining to Colombia, Venezuela, Bolivia, Peru, and Ecuador.

Llorens served as deputy director of the Office of Economic Policy and Summit Coordination in the Bureau of Inter-American Affairs, in which capacity he "contributed to the launch of the historic Free Trade Area of the Americas (FTAA) negotiations in 1998".

[7] During his tenure in Vancouver he created a novel Law Enforcement Hub and opened FBI, Secret Service, ATF, DEA and legacy Customs and Immigration offices at the consulate.

As National Security Council director he drafted and managed inter-agency coordination for a new U.S. policy approach on Colombia (NSPD-18) in the wake of the election of President Uribe.

Following his tenure on the White House staff, Llorens was deputy chief of mission at the American embassy in Buenos Aires, Argentina, until July 2006.

During the coming months he supported the holding of free elections that resulted in National Party standard bearer Pepe Lobo assuming the presidency, and ensure the restoration of the constitutional order.

Llorens diplomatic dispatches released by Wikileaks, caused some controversy in Honduras as Llorens made the case to Washington policymakers that while Zelaya's actions had precipitated the crisis, the United States, as was the case with the broad international community, needed to oppose the illegal and unconstitutional manner in which the seating president was removed from office.

At National, Llorens taught the art and science of "grand strategy" to the elite student body of senior military officers and civilian officials, and led an initiative to strengthen the leadership curriculum at the school.

During his time in Sydney, Llorens was known for his strong advocacy of clean energy, innovation, and the expansion of trade and investment links in the Asia Pacific.

As the special charge d'affaires, Llorens was the senior U.S. diplomat in Kabul directing the largest embassy in the world with a staff of more than 8,500 U.S., Afghan and third country nationals representing 22 U.S. government agencies.

Llorens also worked closely with U.S. and NATO military counterparts, and senior Trump administration officials, including Secretary of State Tillerson, Secretary of Defense Mattis, and National Security Advisor McMaster in developing a new and more robust policy approach on Afghanistan and South Asia formally enunciated by President Trump on August 17, 2017.