The film, Bicentennial Man, starring Robin Williams is a good film to investigate the concept of belonging. He is a robot! in the future who is assigned to a family as their butler (a mechanical Mrs Doubtfire), he craves human love and affection. He wants to be useful and productive. In this, he becomes successful (great American way), and from here, he seeks to be transformed through love - could say, hopes to come to life, through love and become human. It's an unusual movie, but definitely demonstrates belonging and the desire to belong.
Also, Little Miss Sunshine is a great movie for a sense of belonging. What about The Castle?
Good Luck!