Answer:
Through bilateral relationship.
Step-by-step explanation:
Bilateral relationship is a form of diplomatic relations in which two countries can form a cooperative effort to achieve a mutually beneficial goals. Such as engaging in a mutually beneficial trades, being an ally in conflict resolutions with another country , etc.
If we form such bilateral relationships, there will be a huge chance that the people in Cuba can observe the positive effect of Democracy in United States and become more likely to change their perspective. Rather than wars/conflict that often lead to hatred, this would be a more efficient method for United States to promote democracy in Cuba.