Prepare cake batter to fill one cake pan 2/3 full; tint bright red. Pour into prepared pan; bake according to recipe instructions. Cool. Prepare second cake as above, tinting batter blue. Bake according to recipe instructions. Cool. While 2nd cake cools, line pan with plastic wrap; spoon softened ice cream into pan; fill completely, spreading evenly. Freeze until firm.
Remove crown from both cakes. Position blue cake layer on foil-wrapped board. Unmold ice cream and position on top of blue cake layer; trim with knife to fit flush Position red cake layer on top of ice cream layer. Ice cake sides smooth with buttercream. Cover star field area with tip 16 blue stars. Add tip 21 white stars on top. Pipe tip 21 alternating red and white curving stripes on remainder of cake. Add tip 21 star bottom border. Freeze until ready to serve.
Remove cake from freezer 10-15 minutes before serving. Cut and serve.