I would say that the difference is, in part, a matter of scope. American History tends to focus on the history of the United States, beginning largely with the colonial era and tracking forwards towards the present. It's largely a national history. World History, on the other hand, is far more encompassing, both geographically as well as temporally.

The thing is, the history of the world is far larger than any one place—it encompasses the full breadth of human history, starting with the earliest cultures to emerge in the Ancient World—cultures like Egypt, Sumeria, the Indus River Valley civilization in India—before tracking forwards. It covers various different geographical regions as they unfold: China, India, the Mediterranean World, the Americas, Western Europe, and so on, stretching across different time periods on both sides of the Common Era.

There is a significant difference between American History and World History. American History is the study of the history of the United States. It focuses on the development of our country from the days we were colonies of Great Britain to current times. The focus is on what happened in and to the United States throughout our history.

World History takes on a much larger view of events because it focuses on the history of many of the countries or the civilizations around the world. It focuses on major world events that have happened throughout history. World History is much longer than American History. While American History can be traced back to around the late 1400s, World History goes back thousands of years prior to the beginning of American History. Therefore, the study of World History usually requires more time to complete. The study of World History may also view events from a different perspective. The study of American History takes on an American perspective while the study of World History takes on the perspective of people in other countries.

There is a significant difference between the study of American History and the study of World History.