Haiti's initial conquest of East Haiti/the 'Dominican Republic' got the ball rolling. Without that we have no later interventions in Porto Riche, the Leeward Islands, Jamaica, the Bahamas/Turks, etc. Stop that and stop the rest.
Keep Carlist Spain fron trying to overrun the place in the 1860s and it probably remains quite disunited instead of cohesive. That cohesion let it industrialize and fund the University of the West Indies, beginning its meteoric rise with synthetic chemistry, mechanical/electrical/civil engineering, and desalinization techniques. Also if they do not organize the MesoAmerican Trade Block maybe Venezuela, Colombia, Mexico, and Central America focus more on the US and less on themselves. That's one reason the average Haiti has a lifestyle comparable to the average in Northern Italy.