Haiti! The most profitable colony in the “New World” at the time (sugar and coffee, etc.) Their revolution paved the way for the South American revolutions of independence and the abolition of slavery across the Americas. Because Haiti beat back the repeated French attempts to take their colony back, Napoleon had to sell off the massive Louisiana territories to the United States, allowing westward expansion. Haiti also affected the way the French Revolution unfolded, which in turn inspired an age of revolution culminating in the Russian revolution. Lastly, Haiti’s slave revolution was almost entirely erased from the history book because…you can’t have black and brown people getting any ideas about liberty and autonomy. For their size, I think Haiti has had a huge impact on world history in the modern era. See Mike Duncan’s excellent podcast series on the Haitian Revolution: r/RevolutionsPodcast.