What weaknesses in both the US Army and Navy did the Spanish American War reveal?

The Spanish American War was fought in 1898. The United States became involved in the war when Cuba, after several earlier failed revolutions, was attempting to become free of Spain. As a result of the war, the United States gained control of Cuba, Puerto Rico, Guam, and the Philippines, and the U.S. paid the Spanish $20 million. While many Americans were initially very enthusiastic about fighting in the war, which Secretary of State John Hay...

The Spanish American War was fought in 1898. The United States became involved in the war when Cuba, after several earlier failed revolutions, was attempting to become free of Spain. As a result of the war, the United States gained control of Cuba, Puerto Rico, Guam, and the Philippines, and the U.S. paid the Spanish $20 million. While many Americans were initially very enthusiastic about fighting in the war, which Secretary of State John Hay called "a splendid little war," the American armed forces were largely underprepared at the war's start.

The war began when an American battleship called the Maine, which was stationed in Havana's harbor in Cuba, mysteriously exploded. The Americans quickly blamed the Spanish (though there is evidence that the ship's explosion may have been caused by a boiler accident), and the cry "to hell with Spain, remember the Maine" whipped up public support for the war, as did the headlines and photographs that newspaper magnates William Randolph Hearst and Joseph Pulitzer ran in their papers. 

The U.S. Army at the time had too few people and materials and was far from the fighting shape it would be in by the time of the United States' involvement in World War I. Since the Civil War, the U.S. military had mainly been involved with fighting Native Americans on the frontier, and they lacked the light-weight uniforms and other equipment they needed to fight in the tropics. American troops were largely unprepared for the tropical heat and diseases they would encounter in the Caribbean. In addition, the army did not at first have enough troops to fight, but they were able to raise troops though volunteers and by using the National Guard. After they had defeated the Spanish, in part because the Americans were closer to Cuba and could resupply their troops more easily than the Spanish could, the United States embarked on a period in which it defined itself as a world power with a military to match.