Final answer:
The USS Maine explosion and sensationalist journalism, which led to public pressure, were the two primary triggers for the U.S. declaring war on Spain in 1898. The war culminated in Spanish surrender and marked the U.S. emergence as a colonial power.
Step-by-step explanation:
The two main sparks leading the United States to declare war on Spain in 1898 were the explosion of the USS Maine in Havana harbor and the media's influence in swaying public opinion towards war. The sinking of the USS Maine, which was initially blamed on a Spanish mine, resulted in a loss of American lives and generated a surge of anti-Spanish sentiment. This event was augmented by sensationalist journalism, known as 'yellow journalism,' which played a significant role in stirring public and political support for intervention in Cuba. Newspapers led by publishers like William Randolph Hearst and Joseph Pulitzer dramatically exaggerated Spanish atrocities and used the rallying cry 'Remember the Maine, to Hell with Spain!' Ultimately, President McKinley, who had endeavored to maintain neutrality, saw no option but to engage in conflict due, in part, to the public outcry following the Maine incident and the resisting of Spanish reforms for Cuba. Congress declared war on Spain on April 25, 1898, after recognizing Cuban independence and authorizing the use of military force.