Almost from the beginning of its history, America has struggled to find a balance in its foreign policy between narrowly promoting its own security and idealistically serving the interests of others; between, as we’ve tended to see it in shorthand, Teddy Roosevelt’s big stick and the ideals of Woodrow Wilson. Just as consistently, the US has gone through periods of embracing a leading international role for itself and times when Americans have done all they could to turn their backs on the rest of the world.