How did some american politicians justify u. s. imperialism at the end of the 19th century? pls asap

American Imperialism is the true economic, military, and cultural influence of the united states on other countries. Such influence also goes hand in hand with expansion into foreign territories. Expansion on a grand scale is the primary objective of an empire, a notable example being the British empire. The concept of an American Empire was first popularized during the presidency of James K. Polk. 
Meaning,
-they felt they needed to keep up with Europe -they needed more military bases and support-they wanted to spread democracy-they wanted to spread christianity-they wanted to promote unity -they needed more power -they needed port access for trading/military