The USA has a lot going for it.

First off, its huge. The USA is the 3rd largest country on earth, both by population and landmass. This has been true since the industrial revolution spread to the USA. There are a lot of people to work, and a lot of people buying things, both of which are needed to fuel the economy.

The USA also sits on massive deposits of natural resources, meaning that almost everything needed for production, from coal and oil, to iron and copper, could be purchased within the USA. This meant more money to American businesses, which in turn went to their employees, who bought the goods produced. In really basic terms, the USA economy was fueling itself and getting bigger and bigger.

The USA was also an early adapter. The industrial revolution really started in Britain, and one of the first places it spread was the US. This gave the US an advantage over late adapters, and still does. The USA is fully industrial, and has things like paved roads and cell towers throughout the entire country. Countries like Italy, Spain, and Russia for example, were late to the industrial revolution. They are still largely rural/agrarian countries, with concentrations of industrial in certain regions.

Theres also the fact that the USA is the strongest and most populous country on its continent, a continent which is also the most stable in the world. Countries such as Germany, the UK, and China, which have all been rivals of the USA, are not. All 3 were devastated by the world wars and other conflicts, while the USA remained largely unharmed. The country also has a very stable government, which promotes commerce as the economy is (relatively) stable, and protected by the government.

Unlike most other countries, the USA has had around 250 years of a relatively stable economy. There have been downturns, such as 1929, 1970's, and 2008, but because of America's stability, and all the factors mentioned above, the economy was always able to bounce back even stronger.