Talk about the characteristics of American topography.

The topographical features of the United States can be summarized as "three consecutive topographic units, with low mountains (Appalachian Mountains) in the east, vast plains (including the central plains and the Mississippi Plain) in the middle and tall mountains (including the Rocky Mountains, the Sierra Nevada Mountains and the coastal mountains) in the west.

In addition, in the topography of the United States, the plain area is vast, the soil is fertile, and irrigation is convenient, so agriculture is developed, which is a major foundation for the rapid economic development of the United States and its becoming the number one superpower.