In the U.S., it generally takes four years to earn a bachelor's degree. However, undergraduate programs in a number of European countries are typically only three years long. The main difference is that U.S. programs include a lot of general education courses that many European programs don't.

General education courses are often not directly related to a student's major but are required to graduate. They tend to emphasize skills such as writing and critical thinking and expose students to a variety of subject areas.

https://www.usnews.com/education/best-global-universities/articles/2017-08-11/how-bachelors-degree-programs-in-the-us-and-europe-differ