Why was the spanish american war considered a turning point in american history

The brief war fought against the Spanish Navy and land forces in 1898 established the United States as a global, major navy and military power.

The war was fought in Cuba - the Caribbean - and in the Pacific.  If a century before American governments were not willing to join wars among European powers and pursued a cautious diplomacy, full industrialization, territorial expansion and a fantastic growth of economic might made the United States a player in world affairs to be reckoned with a century later. That´s why the Spanish-American war is a turning point in American history: the US would play a large role in world affairs from that moment on.

a. competition with other nations.