1. Liberal Arts Education
One of the major differences between American and European colleges/universities is the fact that American schools allow students to enjoy a liberal arts background. In the U.S., as you know, students do not immediately begin career-focused education (like law, medicine, business, etc.).
For example, some schools like Columbia University require students to take a "Core Curriculum" including courses such as Literature Humanities and Contemporary Civilization. Other universities (like the University of Chicago) have similar course requirements.
This is great for students who do not yet know what career path they would like to pursue.
2. American campus life
Most students live in dormitories in a community of peers. They live away from home and have more independence than students who continue to live at home (as is the norm in Europe). They also enjoy literally hundreds of extracurricular activities on campus and have university funding to explore their interests and passions.
3. Relationships with professors
Smaller class sizes are generally more available at American schools. Professors are required to hold office hours, and they encourage students to stop by to ask any question they like. Juniors and seniors are generally able to take seminars with fewer than ten students.