In a mixing bowl, combine graham cracker crumbs, melted butter, and powdered sugar. Mix until well combined.

Press the mixture firmly into the bottom of a 9x13 inch baking dish to form the cake base.

In a separate bowl, beat the softened cream cheese until smooth.

Add the chilled heavy whipping cream, granulated sugar, and vanilla extract. Whisk until the mixture is fluffy and holds peaks.

Spread the cream cheese mixture evenly over the graham cracker base.

Arrange the sliced strawberries in a rectangle on the top left corner to create the stripes of the flag.

Place the blueberries in the top left corner to represent the stars.

Top with whipped cream if desired and refrigerate for at least 2 hours before serving.