In 1880, he visited Minnesota and became involved with Bishop Ireland's scheme to settle poor Irish people in the State, recently vacated by the Eastern Dakota.

The article explained that John Sweetman was the managing director of the Irish-American Colonization Company, "the principal organizer and practical director of the emigration...in order to make the most profitable selection of lands Mr Sweetman travelled through and carefully examined the States of Dakota and Minnesota, and also Manitoba, and finally purchased some 20,000 acres (80 km²) of prairie land situated in Murray County ...".

The Times of 3 June 1892 mentioned that "Mr John Sweetman of County Meath, who had contributed £1,000 as a donation to the fund for starting the National Press, had been unanimously selected for the Eastern Division".

[6] At the general election in July 1895 he stood in North Meath, where he narrowly failed to unseat the sitting anti-Parnellite MP James Gibney.

Unfortunately, they had not the power to call down the ten plagues of Egypt upon the English Government, but they could boycott England's manufactures and her Navy and Army".

Sweetman practised a form of "clericalist catholicism" and was socially conservative, a stance that lead him to reject any idea of class politics (whether forwarded by Land Lords or Socialists), and to declare in his writing that the only way by which Ireland could be a prosperous nation was if the political class in Ireland cultivated a "national feeling" of unity that brought people of all backgrounds together into a joined social contract.

Sweetman opposed Jim Larkin and the Irish Transport and General Workers' Union during the Dublin lockout of 1913, voicing his views in a pamphlet entitled "The industrial problem".

He declared that World War I had begun when Britain attacked Germany to grab German trade, that Ireland would be ruined by wartime taxation unless it cut ties with Britain and that if he was arrested for ‘speaking the truth’ this would prove the falsity of John Redmond's claim that Ireland had regained her freedom.

[8] He also opposed plans to build a Catholic Cathedral in Merrion Square, where he himself lived, on the grounds that this would cause great trouble and inconvenience to the residents.