During your studies in America you will incur other expenses, just like in the Netherlands. Think of leisure activities, your phone bill and flights to the Netherlands. The amount depends on your personal preferences and what you do in your free time.
You can assume that all school expenses are covered by the university, but if you want to score a nice burger from In ‘n Out on the weekends, you will obviously have to pay it yourself. This also applies to trips on weekends, etc.
In general, the other costs are very not too bad because you are on college campuses a lot!