[4] From 1956 to 1963, Bushnell worked as a United States Air Force historian based in Washington, D.C., and New Mexico.
[3][5] He completed his doctorate at Harvard University in 1951 by writing his thesis on the government of Francisco de Paula Santander.
[9] His other major works included The Santander Regime in Gran Colombia, The Emergence of Latin America, and Eduardo Santos and the good neighbor.
[3] His books dealt with such subjects as the Colombian electoral system during the 19th century and foreign relations during the government of former President Eduardo Santos, who ruled from 1938 to 1942.
[3] He published his last article, "Philatelic Feminism: The Portrayal of Women on Stamps of Argentina, Colombia, Cuba, and the United States", shortly before his death in 2010.