In the late 19th century, the main US foreign policy was imperialistic. The US was trying to expand its global reach, taking such places as Hawaii, Guam and the Philippines.
I would say that the main "old" factor was a desire for more wealth and power. The US was pursuing these in a different way than it previously had because it was now looking to colonize other countries rather than to expand its own country. But it was still the same idea.
I see two relatively "new" factors. First was the idea of "white man's burden." The US had had Manifest Destiny before, but not this idea of civilizing other people. Second was competition with other imperial powers. The US had not previously been interested in building an empire outside North America.
There were many factors that shaped American foreign policy in the late nineteenth century. One factor was Congress. William H. Seward, who was secretary under President Lincoln and Johnson had many objectives on his agenda like buying Russia and pushing American trade on countries. Seward also approved naval occupation of Midway Islands in the Pacific. These objectives were successful however many of Seward’s objectives were rejected by Congress. The rejected objectives included getting Caribbean naval bases, building a canal through Panama, buying Haiti and the Dominican Republic, and purchasing the Danish West Indies. Congress also rejected the annexation of Hawaii by James G. Blaine, the secretary for President Garfield and Harrison. So foreign policy depended on approval from Congress. Second, American reactions affected foreign policy by making it more assertive. For example, In Chile, US sailors were involved in a brawl that left some dead, some injured and others in jail. There was an outburst of bellicose nationalism in the US so President Harrison threatened military retaliation. He only relented when Chile apologized and paid an indemnity. There are many other instances like during a boundary dispute between Great Britain and Venezuela.