Final answer:
The U.S. declaration of war on Spain in 1898 marked America's entry into the Spanish-American War, showcasing its interventionist approach and signaling its emergence as a global power after gaining several Spanish territories.
Step-by-step explanation:
The United States declaration of war on Spain in 1898 is an example of interventionist foreign policy and the beginning of the Spanish-American War. The war came to represent a critical milestone in America’s development as a global power. Driven by a zeal for expansionism, the United States intervened in Cuba's fight for independence, leading to the Philippines, Guam, and Puerto Rico coming under American control after Spain's defeat. This shift significantly altered the balance of power at the turn of the twentieth century and marked the end of Spain as a colonial power while initiating the United States' rise as an imperial force.