In medium bowl, combine American Cheese and flour; set aside.
In a medium saucepan cook green pepper in butter just until tender but not brown; stir in wine. Heat slowly, over low heat just until bubbly. Gradually add shredded cheese and flour, stirring constantly until smooth.
Stir in cream cheese and mustard; continue to stir over low heat until smooth. Transfer to fondue pot. Keep warm.
Cut up French Bread or serve with Breadsticks.