She served as acting Assistant Secretary of State for East Asian and Pacific Affairs during the first Trump administration.

[4][5] Prior to joining the State Department, Thornton worked at the Foreign Policy Institute where she studied and wrote about Soviet politics and contemporary Russia.

She has previously served as the Principal Deputy Assistant Secretary for the Bureau of East Asian and Pacific Affairs (EAP) since February 2016 and before that, she worked as the Deputy Chief of Mission to the United States Embassy in Ashgabat, Turkmenistan, Deputy Director of the EAP Office of Chinese and Mongolian Affairs, Economic Unit Chief in the EAP Office of Korean Affairs.

[8] Susan Thornton retired in August 2018 after then-Secretary of State Rex Tillerson stepped down.

"[10] In particular, US Senator Marco Rubio (R-FL) stated that he would do all he can to prevent Susan Thornton from being confirmed.