Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.

In a large mixing bowl, sift together the flour, baking powder, and salt.

Cream together the unsalted butter and granulated sugar using an electric mixer until pale and fluffy.

Add the eggs one at a time to the butter-sugar mixture, mixing well after each addition. Add vanilla extract.

Gradually alternate adding the dry ingredients and the milk to the creamed mixture, mixing on low speed until just combined.

Pour equal portions of the batter into the prepared cake pans and bake for 25-30 minutes.

Let the cakes cool in the pans for about 10 minutes before transferring to a wire rack to cool completely.

Beat the softened unsalted butter and gradually add the powdered sugar, followed by vanilla extract and heavy cream.

Assemble the cake by spreading buttercream between the layers and around the sides. Apply a final layer of buttercream over the entire cake.

Decorate with fresh berries arranged in the design of a flag and chill for at least 30 minutes before serving.