He joined the Department of State in 1991 as a presidential management intern in the Bureau of Political-Military Affairs and for more than a decade served in a variety of key positions.

From 1994 to 1996 he was a special assistant to Ambassador-at-Large Robert Gallucci, providing analysis of the negotiation and implementation of the U.S.-North Korea Agreed Framework.

[1] From 2001 to 2004, he served on the NSC staff as director for regional affairs in the Office of Combating Terrorism where he focused on Middle East, Southeast Asia, and related counterterrorism issues in the period after September 11, 2001.

"[2] In October 2020, Rasmussen signed a letter stating that the Biden laptop story “has the classic earmarks of a Russian information operation.

He is the recipient of numerous awards, including the National Intelligence Distinguished Service Medal in 2017, the Distinguished Presidential Rank Award in 2016, an International Affairs Fellowship from the Council on Foreign Relations, and has taught a course on U.S. counterterrorism policy at Georgetown University's School of Foreign Service.