The Americas are a huge region and therefore their physical geography is extremely complex. We only have space here for a very cursory discussion of this topic.
We can start by saying that the Americas stretch from north to south more than from east to west. The distance from the northernmost point to the southernmost point is about 8700 miles. There are two large continents, North America and South America, connected by a relatively thin band of land that we call Central America.
Perhaps the main feature of the physical geography of the Americas is the massive mountain range that runs down its west side. These mountains are called the American Cordillera and include such ranges as the Rockies in North America and the Andes in South America.
The east side of the Americas is much flatter and is home to many large river basins. These include the Mississippi in North America and the Amazon and the Rio de la Plata in South America.
The northern and southern extremities of the Americas are polar and therefore very cold. In North America, there is extensive tundra at the northern extreme. There are also major deserts in the middle of the Americas, including deserts in the American Southwest and in Mexico.
Of course, a comprehensive discussion of the physical geography of the Americas would need much more than this brief discussion.