The United States had a goal of becoming a world power in the late 1800s and early 1900s. To become a world power, people believed our expansion was justified. In order to be a world power, we needed to spread our influence around the world. In order to do this, we needed places where our navy could stop and get refueled and resupplied. Colonies allowed for this to happen.
We also needed colonies to help our businesses grow. Colonies could provide us with raw materials cheaper than we could get them if we bought them from other countries. Colonies also provided our businesses with a place to sell their products. Being a world power meant we needed to have a strong economy. Colonies helped us develop a strong economy.
Other countries were controlling lands overseas. If we waited much longer, there would be fewer opportunities to gain land. As it was, we had to go to war with Spain in order to gain possessions beyond our borders. We wouldn’t be on the same playing field with other world powers if we didn’t expand and get colonies.
Thus, if a person believed the United States should be a world power, they would have supported our expansionist policies.