As the world’s most powerful country, the United States is not only very strong economically but also technologically. So I think the reasons behind this are multi-faceted.

In World War I, the United States achieved a great victory. The war weakened the European powers, while the United States' economic and military strength was enhanced. During World War II, the war stimulated the rapid development of American industry and greatly enhanced its economic strength. Moreover, the United States began to develop atomic bombs very early, and its military strength was strengthened.

We all know that the political, economic and military strength of the United States is second to none in the capitalist world. In the early 1990s, with the disintegration of the Soviet Union and the end of the Cold War era of confrontation between the United States and the Soviet Union, the United States had no challengers or competitors and became the biggest beneficiary and the world's only superpower.

However, the superpower the United States possesses in the world is not only reflected in its military power. At that time, its economic strength exceeded that of West Germany to a large extent. At the time, West Germany had the largest economy in Europe. By the 1990s, the U.S. economy was far ahead of any other country in the world. Entering the 21st century, the U.S.'s GDP, calculated at the then dollar exchange rate, accounted for one-third of the world's total and was twice the combined GDP of Japan and China.

The reason why the United States can become a hegemon depends on many reasons, including the military and the rapid development of American industry.