When looking at various power rankings by country, mainly ranked by the size ouf the output of the whole economy, the United States of America have been the number one for decades now. With its GDP exceeding 21 trillion dollars this year, the U.S. has the largest annual economic output in the world. However, when observing the public debt of this country, it is easy to conclude that the U.S. is deeply in debt. When looking at the ratio of the country's GDP and its total government debt, the fiscal situation does not seem so optimistic. This paper gives an insight on not only the structure and size of the debt of the U.S., what are its components and who owes the debt. The debt ceiling is also defined in this paper, showing what are the effects of the raising public debt of the country and how U.S. government faced several debt crises. Additionally, this is paper warns of the consequences of such actions and explain what a high and rising public debt can do to an economy. To give a more realistic view on the public debt of this country, one chapter compares the U.S. public debt to the debt of several countries that are also known as world powers: China, Russia and the EU. The question of sustainability of the U.S. public debt is discussed and the way its government tries to keep it under control as well.