In my personal opinion it strengthened the identity, and led people to believe that United States were invincible. Since the Monroe's doctrine one of the goals of United States was to prevent Europeans to interfere in the affairs on the American continent. Therefore, defeating Spain, country that was once a great colonial power proved to Americans and the public that no one can match United States.
Explanation:
Spanish-American war proved the strength of US army, that wasn't involved in major conflicts for decades. Therefore, this led to belief that country should spread its imperial claims.
