Jim Pinkerton ironically lays out the rules for effective imperialism over at The American Conservative. Among them:
Effective Imperialists must combine ethnic and linguistic "ground truth" with high Machiavellianism. To keep control of India, for example, the British cultivated the Sikhs as a ruling elite. Why? Because the Sikhs were a tiny minority. Once they were installed in the upper reaches of the Raj, the Sikhs were anxious for the Brits to stay, so as to preserve their top-dog status. That approach proved Effective for a century.
By contrast, today, is there any American clever enough to see the wisdom of dividing Iraq into three parts, so as to make all three mini-states–Sunni, Shia, Kurd–dependent on the U.S. for border protection? Evidently not.
Whole thing here.
He also mentions this 2003 Carnegie Endowment for International Peace study of the U.S.'s various attempts at nation-building. The short scorecard? Of 15 instances (not counting current interventions in Iraq or Afghanistan), only four succeeded, with success being defined as "democracy after 10 years" of U.S. involvement. Whole thing here.