North American history begins with the spread of people from East Asia across North America. Those people then divided into various tribes with different languages - we call them Native Americans.
Just before 1500 AD, people began to spread into North America from the opposite direction - from Europe across the Atlantic Ocean. These new people gradually killed off most of the Native Americans, and started the United States of America.
Today, Native American people are beginning to spread out across North America again. Many are coming north from Mexico and from South America, and they are already in the majority in some Western states (where we call them Hispanics or Latinos). There are more and more Hispanic people across the South as well as the West, and probably by about 2050 there will be more Native people than European people in North America again.