The United States loves to help people, and that has resulted in some giant non-profit organizations. These have all different purposes so you just have to choose the one that is right for you.
Giving is good in any situation but it really is better to be strategic about your giving. You may consider strategic philanthropy to give in a targeted manner.
The true purpose of sororities are to help raise money for charity and provide young women with sisterhood that can help them to succeed in college and at professional endeavors that happen after college.