The GDP (nominal) of the United States is the biggest in the world by far, even though the Chinese economy has made huge strides forward they are still far behind the United States GDP.
The GDP of this North American country accounts for more than 20 trillion USD, which around 6 trillion more than the second placed China, and more than three times more than the third placed nominal GDP of Japan.
On the other hand, the GDP per capita tells another story, as the United States, despite the fact that they have the biggest nominal GDP in the world, actually have the 19th biggest GDP per capita, trailing way back than the first placed Liechtenstein by than then two and half times.