Cuba
In the late 1800s, people in Cuba did not want to be under Spanish rule. Therefore, many fled to Florida. They still strongly supported Cuba's independence even though they didn't reside there anymore. The U.S. had invested money in Cuba, had citizens living there, and traded with them, so they decided that they would side with Cuba in this war. Things got personal when a U.S. warship blew up off the coast of Havana, Cuba. The U.S. blamed Spain. Thousands of Americans went over to Cuba and fought for it's independence. In the end, Cuba gained it's independence.
The Philippine Islands
While fighting for Cuba, the U.S. used the Philippine Islands as a naval base. With encouragement from the U.S., the Filipino rebels stood up against the Spanish as well. They were able to declare their independence from Spain and expected the U.S. to recognize them as independent. However, the United States gained control of the Philippines. Although the Filipinos tried to rebel against their second imperialist country, the United States easily crushed them, and took control of the islands.