Answer:
The correct answer is a combination of different factors actually and not only one factor.
Explanation:
The land, the weather conditions, the increasing population thanks to the inmagration, the abundant presence of rivers that can be navigable and the great amount of natural resources. All of these factors influence the posibility of America to have a greater intensive farming overpassing other countries.
Later, during the First World War, The United States increase their number of exports related to the arms industry. Since then, and after join the war, America became the first great power in the world.
