Manifest Destiny is the belief that Americans were destined to expand across North America from coast to coast.
The Emancipation Proclamation is an executive order by Abraham Lincoln freeing the slaves.
The Monroe Doctrine was a United States policy of opposing European colonialism into the Americas.
Lastly, The Louisiana Purchase was the purchase of the Louisiana territory by the US from France.
Manifest Destiny is the best answer.
The Marshall plan helped in stopping the communist aggression and expansion in Europe during the Cold War by establishing a global trade wherein it emphasizes "free market" and "encourage European peace." The plan helped to economically sustain and stabilized the war-torn countries in Europe.
United States participation in the ICC treaty regime would also be unconstitutional because it would allow the trial of U.S. citizens for crimes committed on U.S. soil, which are otherwise entirely within the judicial power of the United States.
