Preheat oven to 350ºF. Do not grease 9-inch by 13-inch pan.
Mix angel food cake mix according to package instructions (the one I used only required water). Pour into ungreased pan and bake until firm to the touch, about 30 minutes. If the center still jiggles, bake it 5 minutes longer.
Cool completely, at least 1 hour. Using a fork, pierce cake in rows about 1/2-inch apart. When the fork becomes sticky, dip tines in water to clean (typically at the end of each row).
Pour Jello into a medium bowl and whisk in boiling water. When Jello is dissolved, stir in cold water. Drizzle over the entire surface of cake. Cover and refrigerate at least 3 hours or overnight.
In a large bowl, or in a standing mixer fit with the whisk attachment, combine pudding and milk until well blended. Gently fold in whipped topping.
Spread frosting on cake and arrange berries on top to resemble an American flag. Store in refrigerator.
Adapted from Pillsbury Easy Meals magazine, July 2005 edition.