He served as the United States Ambassador to France from 1949 to 1952, United States Ambassador to West Germany from 1957 to 1959, and United States Ambassador to the United Kingdom from 1961 to 1969. He was an American envoy at the Paris peace talks between the United States and North Vietnam in 1970 and 1971. Bruce also served as the first United States emissary to the People's Republic of China from 1973 to 1974. He was the ambassador to the North Atlantic Treaty Organization from late 1974 to 1976.