Irish Americans were powerful in the Democratic party , and groups such as Clan na Gael opposed going to war alongside their enemy Britain , especially after the violent suppression of the Easter Rising of 1916 . Wilson won them over in 1917 by promising to ask Britain to give Ireland its independence . Wilson had won the presidential election of 1916 with strong support from German-Americans and Irish-Americans , largely because of his slogan " He kept us out of war " and the longstanding American policy of isolationism . At the Paris Peace Conference in 1919 , however , he reneged on his commitments to the Irish-American community , and it vehemently denounced him . His dilemma was that Britain was his war ally . Events such as the anti-British Black Tom and Kingsland Explosions in 1916 on American soil ( in part the result of wartime Irish and German co-ordination ) and the Irish anti-conscription crisis of 1918 were all embarrassing to recall in 1920
Black Tom
Black Tom explosion
1920 United States presidential election