Preheat the oven to 350°F (175°C). Grease and flour a 9x13 inch baking dish.

In a large mixing bowl, combine the white cake mix, 1 cup of water, vegetable oil, and eggs. Mix until well combined.

Pour the cake batter into the prepared baking dish and bake according to package instructions, usually about 25-30 minutes, or until a toothpick inserted in the center comes out clean.

Once the cake is baked, allow it to cool completely in the pan on a wire rack.

In a separate bowl, dissolve the strawberry Jell-O in 2 cups of boiling water. Stir until fully dissolved, then add 1 cup of cold water. Let it cool for a few minutes.

Once the cake is cooled, poke holes all over the top using a fork or skewer.

Pour the prepared strawberry Jell-O mixture evenly over the cake, allowing it to seep into the holes. Refrigerate the cake for at least 4 hours or until Jell-O is set.

Once the Jell-O is set, spread the whipped cream evenly over the top of the cake.

Decorate the top of the cake with sliced strawberries and blueberries to create a flag design. Arrange the strawberries in rows for the stripes and place blueberries in the top left corner.

Slice and serve the cake chilled.