Hello! American expansionism during the Age of Imperialism is definitely a controversial topic. I imagine you will find both those who believe that America was right to carve out her own influence among the European powers and those who do not agree. However, I will present the facts below so that you can make an informed decision.
Was American expansion overseas from 1880-1920 justified?
The aftermath of the Spanish-American War: after the Spanish-American War, the United States annexed the Philippines and Hawaii. The Spanish also gave up their claims to Guam, Cuba, and Puerto Rico. How is this important? The Philippines were a stepping stone to China; a base of operations there made it easier for the United States to monitor the situation in China. This was necessary because European powers like England, France, Russia, Germany, and Japan already had imperialistic desires in this direction.
China: The United States wanted to protect its interests in the region and its leaders pushed for an Open Door Policy. In a nutshell, this policy prevented any one European power from asserting its influence above that of the other nations in China. In fact, the United States pushed for China not to be carved out into various European colonies after the Boxer Rebellion; in return, China would trade with all the European nations. What did the US get out of this? China provided inexpensive raw materials to support and grow American industry. Think American cars, manufacturing, railways, etc.
Dominican Republic: Two American presidents made some important decisions in Latin America. President Roosevelt, who advocated a strong international presence ("Speak softly and carry a big stick"), cleverly protected American interest by stepping in when the Dominican Republic was awash in foreign debt. In exchange for assuming the debt, America controlled Dominican import duties for two years. President Taft's Dollar Diplomacy favored business over bullets: he encouraged American business investment in countries like the Dominican Republic for the purposes of strengthening American influence around the world and promoting worldwide stability.
Hawaii: Most American expansion elicited scant support from the native peoples of these countries, none more so than in Hawaii. Like the Chinese, the Hawaiians greatly resented American intrusion into their government, their country, and their way of life. Hawaii was clearly annexed because of the economic and strategic benefits it provided to American security and business.
Mexico: Not every US president favored expansion for the purposes of merely protecting US interests. In Mexico, American business interests led to support for the brutal dictator General Victoriano Huerta. The general seized power in Mexico in 1913. American businesses favored this unyielding dictator because he mercilessly crushed any form of dissent. Why was there so much dissent in Mexico at this time? Most Mexicans were poor; their desperate lives led them to agitate for better conditions and better opportunities.
Their despair led to the Mexican Revolution in 1910. That's what American businesses did not want; they were more interested in protecting their investments. President Wilson was aghast at this selfishness. He wanted Mexico to have better leaders and thought he was the man to make that happen. However, he was not successful (not for lack of trying); the leaders the President tried to set up would not always do what he expected of them.
Note: You can find more information on whether US expansion was justified between 1880 and 1920. It is really a lesson plan for high school teachers, so ignore pages 1 and 2; from pages 3 to 17, you will find fantastic information to work with. I discussed the four countries above because they provided great facts on why America chose to compete with European powers on the world stage during the Age of Imperialism. World conflict has existed since the dawn of time. It is a sad fact of life and a sobering commentary on human nature that force has been necessary in acquiring all the many economic benefits we have come to enjoy and appreciate today.
Did the press cause the Spanish-American War?
The short answer is no. The long answer:
The term "yellow journalism" originated from a competition between two publishers, Joseph Pulitzer and William Randolph Hearst. Yellow journalism is really sensational reporting for the purposes of selling newspapers. Although the two publishers did not misrepresent facts in their reporting of the Cuban fight for independence, they did make sure to focus on the suffering of the Cuban people under Spanish rule and the atrocities committed by the Spaniards in Cuba. This kind of laser focus by the publishers elicited great sympathy for the Cuban revolutionaries, and even better for the publishers, made a lot of money.
When the American ship the Maine sunk off Havana harbor, the two publishers insinuated what most regular Americans were already thinking. Why, the Spanish sunk the ship! The US Navy then investigated and found that the explosion likely originated from a mine in the harbor. The publishers seized on this announcement to call for war. Did the publishers influence public sentiment against the Spanish? Sure. But the suspicion and distrust Americans felt toward the Spanish were already there. Consider that the Spanish were after the same colonies that the Americans were after. So, although yellow journalism did help create public support for the Spanish-American war, it did not cause it.
Thanks for the question!