President Barack Obama nominated Campbell as U.S. Ambassador to Mongolia on March 5, 2012 and the U.S. Senate confirmed her on June 29, 2012.[6] She was sworn in on August 6, 2012, and presented her credentials to President Tsakhiagiin Elbegdorj on August 24, 2012.[citation needed]
Campbell characterized her tenure in Mongolia as "steering the U.S. government interaction with Mongolia, driving that relationship through a change, a transition."[5] She has stated that there were three main areas upon which she wanted to strengthen ties between the U.S. and Mongolia; broadening commercial development, military and development cooperation, and cultural cooperation.[7]
Campbell's tour in Mongolia ended in 2015.[8] She then served as an assistant professor for National Security Studies at the National War College until 2017. After that she was put in charge of the recruitment and examination of new Foreign Service Officers plus some other internal State Department programs until mid-2018, when she was posted to USASEAN.[1] She left the State Department in 2019, and joined American University's School of International Service in 2020. She became a full-time faculty member and administrative director of SIS's graduate programs on U.S. Foreign Policy and National Security (USFP) and Global Governance,
Politics and Security (GGPS) in July 2022.[9]