Wrong was first secretary in the new Canadian Embassy in Washington, DC, starting in the late 1920s, and served in the League of Nations. In 1938 he represented Canada at the Evian Conference. Wrong went to Washington as ambassador in 1946 and held that post until 1953. He was one of the key architects of the North Atlantic Treaty, which would give rise to NATO. He later rose to become the Canadian Secretary of External Affairs was named undersecretary to NATO, but died before he could take up the post. Wrong devised and honed the idea of functionalism, a principle which argued that in those areas in which Canada had the resources of a great power – food, minerals, air power – she should be treated like a great power. Functionalism became the basis of Canadian wartime policy, and to it must be credited much of the gains in Canadian influence and prestige.
Quotation from "The Gentle Nudge: The Canadian Department of External Affairs and the North Atlantic Treaty, 1948–1949" by Michael W. Manulak:
Wrong was the “the most incisive of the senior officials” in his thinking and the “crispest” in his writing. He was long described by Norman Robertson as “the most able man in the service.” Wrong was considered “brilliant” although “somewhat on the assertive side”. This assertive side could border on impatience or waspishness. In diplomacy, Wrong was of a very practical and organized nature, seeking clear Canadian interests with fewer abstract notions or moral preoccupations. Wrong was extremely well-connected with the State Department and highly respected. Hickerson described him as “one of my best friends.” Wrong was also a close personal friend of Dean Acheson (US Secretary of State from January 1949)in a relationship that dated back to their childhood.