I'm not sure why people wish to equate the United States with being an empire. Empires are very specific entities with very typical structures, and the United States does not fit the description.
What the U.S. has is a growing population 303,800,000 people. It is the third largest country in the world by area, and the third largest in terms of population. It possesses the most powerful military force. It has the largest and most technologically powerful economy in the world. The per capita GDP is about $46,000 US. It's the leading industrial power in the world that is both highly diversified and technologically advanced. Items produced include refined petroleum products, steel, motor vehicles, aerospace, telecommunications, chemicals, electronics, food processing, consumer goods, lumber, mining and cultural products. The U.S. possesses a large, technologically advanced multipurpose communications system, and produces 4.167 trillion kWh of electricity.
Natural resources mining and production includes copper, lead, molybdenum, phosphates, uranium, bauxite, gold, iron, mercury, nickel, potash, silver, tungsten, zinc, petroleum, natural gas, timber. The US has the world's largest coal reserves with 491 billion short tons, accounting for about 27% of the world's total.
In terms of agriculture, the United States produces wheat, corn, other grains, fruits, vegetables, cotton, beef, pork, poultry, dairy products, fish, and forest products. It's the world's largest exporter of agricultural products. In fact, agriculture in the United States is roughly 2.6 times more productive than it was in 1948.
All of that makes it quite powerful. Barring extreme and unforseen change, it still will be a major power in twenty-five years.