Spain was initially one of the more powerful countries in Europe especially with her acquisition of colonies. However as time passed, Spain's power waned and United States saw this as an opportunity to show her power. Initially, the United States wanted to protect her interests in Cuba, which was a Spanish colony, and this eventually led the United States to declare war against Spain.
Afterwards, the United States captured the Philippines, where the Spanish-American War of 1898 took place. The war only lasted 6 weeks and a treaty between the United States and Spain was signed. In this Treaty of Paris, Spain agreed to free Cuba, and to cede Guam and Puerto Rico to the United States. It was also agreed that the Philippines will be bought by the United States for $20 million. With the acquisition of these colonies, the United States began to rise into power in the international scene.
During World War I, the United States remained neutral until 1917, when she decided to join the war as an ally of the Allied Forces (Triple Entente: United Kingdom, France, and Russia) against the Central Powers (Germany, and Austria-Hungary). By the end of the war, the United States became acknowledged internationally as a superpower too.
