I came across this quote in Josiah Royce's California: A Study of American Character (1886). Royce, a native Californian who taught moral philosophy at Harvard, was reflecting on the events leading up to statehood. After concluding that General John C. Fremont hadn't covered himself in glory during that time, Royce offered the following thought.
The American as conqueror is unwilling to appear in public as a pure aggressor ... The American wants to persuade not only the world but himself that he is doing God service in a peaceable spirit, even when he violently takes what he is determined to get (p. 119).