Answer:
A- The Spanish-American war was started from the sinking of the USS Maine in Cuba, during the Cuban war of independence, by the Spanish. In response to this unjustified attack, the United States demanded the withdrawal of Spain from Cuba immediately, and the recognition of the independence of that country. Given the Spanish refusal, the United States entered the war to help Cuba achieve its independence.
B- The United States entered the war seeing the opportunity to displace Spain as a colonial power in the Caribbean. A presumably easy victory would make the United States with control of Cuba and Puerto Rico, thus dominating the adjacent sea to the American coasts, guaranteeing national security and at the same time expanding the sphere of influence towards Latin America, consistent with the provisions by the Monroe Doctrine.
C- The Spanish-American war meant a new period in the history of the foreign policy of the United States, since from this moment, the European influence on the American continent became minimal. In turn, the United States began to expand into the Pacific Ocean, thus becoming a nation with a relevant strategic and military weight for the time, thus beginning a period of predominance in international negotiations. The Philippines and Guam became two strategic positions from which America not only exercised dominance over the western hemisphere, but also began to influence Asia and Oceania.