The dubious logic behind Bush's adventure in Iraq was that if an evil dictator was overthrown, democracy would flourish. The supposed exemplars of this notion were post WWII Japan and Germany. This naive expectation ignores the fact that neither Japan nor Germany was a complete stranger to democratic institutions and that the Allies, mostly the US, imposed long occupations on both defeated nations in which democratic institutions were carefully nourished and deviations rigorously suppressed.
Bush's slapdash attempts predictably failed in Iraq and Afghanistan, but the time since has seen a number of more or less spontaneous dictatorial overthrows in Tunisia, Libya, Egypt as well as a failing attempt in Syria. Most of these have been disasters. The pattern is hardly different in the dozens of former colonies that were turned loose with superficially democratic institutions by the European powers. With very few exceptions, democracy has failed in them.
This should remind us of the point that the republic is a fragile flower, and one that can only thrive in very carefully cultivated soil. As a minimum, a system of laws and a sense of nationhood seem to be required. Tribal societies almost utterly lack these.
The exceptions are very interesting. India is one of the very few that made the transition from colony to almost seamlessly, albeit with some bumps in the road. Taiwan and South Korea went from dictatorship to democracy in evolutionary fashion, though both had plenty of US influence for both good and ill. Probably more important for both was the presence of a strong and remorseless enemy at the gates.
Which reminds me: the internal enemies of the American Republic continue their relentless work to undermine our sense of common purpose and unity.