In the closing years of the 19th century, the United States began to emerge as a world power.  With the conquest of North America nearly complete, attitudes in the U.S. changed to become much more tolerant of foreign adventures.  The changes, wrought by the industrial revolution and evolving social norms, contributed to a new willingness to engage in imperialistic expansion.  This new version of Manifest Destiny arose from strategic and economic concerns and appeals to religious and emotional sentiments.

Source Link: Chapter 15.  American Military History, Volume 1.  “Emergence to World Power 1898-1902.” https://www.armyheritage.org/75-information/soldier-stories/343-spanishamericanwar