Economic interests did a great deal to encourage American involvement in overseas expansion.
One of the major reasons that some Americans wanted to expand overseas, (for example, by taking control of places like Cuba and the Philippines in the Spanish-American War) was to get more sources for raw materials and markets for American products. They felt that having imperial possessions would give them access to the resources of those possessions. For example, one reason to take Hawaii was because Americans had interests in Hawaii's sugar industry.
So, one major reason for overseas expansion was to help give America access to more resources and new markets.