Since the US had a protracted guerilla war after it conquered the Philippines, I don't think you can say we introduced democracy.
The U.S. established an elected legislature for the Philippines in 1907. In 1916 the U.S. replaced the appointed Philippine Commission with an elected Philippine Senate.
And I don't think the British really did in India either; they were basically thrown out after World War 2, but during the war? They had no problem implementing martial law, or cracking down on the INC before the war.
Britain established elected councils in India in 1909, and partly elected provincial and national councils in 1919. The scope and authority of the elected councils was greatly expanded again in 1935. Britain retained overriding powers for the Viceroy and provincial governors, and imposed extensive constraints on the new assemblies, but the movement toward democratic sovereignty was very considerable. There was much discontent among Indians at the limitations, but the 1937 elections to the councils were hotly contested; the INC won in most of the provinces.