The correct answer to this open question is the following.
I would explain the fact that despite the U.S. being a relatively young country., American citizens have enjoyed a "meteoritic rise in global importance since declaring independence from Britain in 1776. The kinds of advances in the past hundred years in particular, that have established America as a "world leader economically, militarily, and technologically has been the following.
When Europe was fighting in World War I, the United States remained neutral at the beginning. American industries and bankers loaned millions of dollars to European countries and sent supplies to the war front. That made the United States make a lot of money.
As a result of World War I, Europe was in deep debt. And 20 years later, again, another war: World War II. The United States entered the war until December 1941, after Japan attacked the Pearl Harbor base in Hawaii. Again, too much pain and destruction in Europe, while the United States business loaned a lot of money through the Marshall Plan.
From then on, the United States was way ahead of European superpowers. Plus, smart investment in education, industry, business, and technology, has allowed the United States to become of the most powerful countries in the world.
Today, Germany, Japan, and China have come very closed to equal the power of the US.