According to Keith Robbins, he was a widely traveled authority on law, government, and history whose expertise led to high political offices culminating with his successful role as ambassador to the United States, 1907–13.

In 1876 he ventured through Russia to Mount Ararat, climbed above the tree line and found a piece of hand-hewn timber, 4 feet (1.2 m) long and 5 inches (13 cm) thick.

In 1880 Bryce, an ardent Liberal in politics, was elected to the House of Commons as member for the constituency of Tower Hamlets in London.

In 1885 he was made Under-Secretary of State for Foreign Affairs under William Ewart Gladstone but had to leave office after the Liberals were defeated in the general election later that year.

In 1897, after a visit to South Africa, Bryce published a volume of Impressions of that country that had considerable influence in Liberal circles when the Second Boer War was being discussed.

[8] He devoted significant sections of the book to the recent history of South Africa, various social and economic details about the country, and his experiences while travelling with his party.

[14] The "still radical" Bryce was made Chief Secretary for Ireland in Prime Minister Sir Henry Campbell-Bannerman's cabinet in 1905 and remained in office throughout 1906.

[15] Bryce had become well known in America for his book The American Commonwealth (1888), a thorough examination of the institutions of the United States from the point of view of a historian and constitutional lawyer.

Now there is some poverty ... and a greater number of gigantic fortunes than in any other country of the world"[16] and "As respects education ... the profusion of…elementary schools tends to raise the mass to a higher point than in Europe ... [but] there is an increasing class that has studied at the best universities.

"[17] The work was heavily used in academia, partly as a result of Bryce's close friendships with men such as James B. Angell, President of the University of Michigan and successively Charles W. Eliot and Abbott Lawrence Lowell at Harvard.

The appointment, criticised at the time as withdrawing from the regular diplomatic corps one of its most coveted posts, proved a great success.

The United States had been in the habit of sending, as minister or ambassador to the Court of St James's, one of its leading citizens: a statesman, a man of letters, or a lawyer whose name and reputation were already well known in Great Britain.

[24] Bryce's account was confirmed by Vernon Lyman Kellogg, the Director of the American Commission for Relief in Belgium, who told the New York Times that the German military had enslaved hundreds of thousands of Belgian workers, and abused and maimed many of them in the process.

Later, with the assistance of the historian Arnold J. Toynbee, he produced a documentary record of the massacres that was published as a Blue Book by the British government in 1916.

In 1921 Bryce wrote that the Armenian genocide had also claimed half of the population of the Assyrians in the Ottoman Empire and that similar cruelties had been perpetrated upon them.

This notably genial gregarious man had his hates, chief among them illiberal regimes: the Turkish oppressors of Bulgars and Armenians, and, later the Kaiser's Reich in World War I.

[28]Bryce had a distrust of current democratic practices seen as late as his Modern Democracy (1921), which was a comparative study of a certain number of popular governments in their actual working.

During the last years of his life Bryce served as a judge at the International Court in The Hague, and promoted the establishment of the League of Nations.

[8] From his Caucasian journey, he brought back a deep distrust of Ottoman rule in Asia Minor and a distinct sympathy for the Armenian people.

[50] Bryce died while on holiday on 22 January 1922, aged 83, of heart failure in his sleep at The Victoria Hotel, Sidmouth, Devon, on the last of his lifelong travels.

[53] There is a large monument to Viscount Bryce in the southwest section of the Grange Cemetery in Edinburgh, facing north at the west end of the central east–west avenue.