As you can see here, Sen. Mark Kirk (R – Ill.) is working on his advanced courses.
The total surface area of the United States is 3.794 million square miles. This number includes all land and territorial waters.
The total surface area of the Earth is 196.9 million square miles.
3.794 / 196.9 = .01926866429
The United States comprises 1.9 percent of the Earth’s total surface area.