HEAT oven to 375 degrees F. Pour cola in microwave-safe measuring cup or bowl. Let stand, stirring occasionally, while preparing crust. Combine crushed pretzels, sugar and butter until moistened. Press evenly in 8x8-inch baking pan. Bake 10 to 12 minutes or until lightly toasted. Cool completely.
MICROWAVE cola on HIGH 2 minutes or until boiling. Pour over gelatin in medium bowl. Stir gently 2 to 3 minutes until gelatin is dissolved and foam disappears. Stir in black cherry topping. Chill 10 to 15 minutes or until just slightly thickened.
MEASURE 1 1/4 cups whipped topping in small bowl. Add 1/2 cup gelatin mixture, stirring until evenly blended. Spread over cooled pretzel crust. Chill 10 minutes. Spoon remaining gelatin mixture over whipped topping layer. Chill 1 hour or until firm. Top with remaining 1 cup whipped topping.