Prepare USA mold with cooking spray; set aside. In a liquid measure, combine one and half cups cups boiling water and strawberry gelatin powder. Mix until gelatin is completely dissolved. In another liquid measure, combine one and half cups boiling water and blueberry gelatin powder. Mix until gelatin is completely dissolved. Stir in one cold water in each liquid measure. Pour strawberry mixture into prepared mold. Refrigerate one hour, or until set but not firm. Reserve blueberry mixture at room temperature. Meanwhile, stir 3/4 cup boiling water, lemon gelatin powder, and ice cream into a liquid measure. Mix until smooth. Spoon mixture over top, set strawberry mixture in mold. Refrigerate 30 minutes more, or until set but not firm. Refrigerate blueberry mixture 30 minutes, or until slightly thickened. Spoon over top lemon mixture in mold. Refrigerate entire dessert for four hours, or until firm. Unmold and serve.