In a medium bowl, combine graham cracker crumbs, melted butter, and granulated sugar. Mix until the crumbs are evenly coated. Press the mixture into the bottom of a 9x13 inch baking dish to form the crust. Refrigerate for 15 minutes to set.

In a large mixing bowl, beat the softened cream cheese with an electric mixer until smooth. Gradually add powdered sugar and vanilla extract, mixing until well combined.

In another bowl, whip the heavy cream until stiff peaks form. Gently fold the whipped cream into the cream cheese mixture until fully incorporated.

Add the sour cream to the mixture and fold gently until smooth.

Pour the cheesecake filling over the chilled crust, spreading it evenly. Smooth the top with a spatula.

Arrange the sliced strawberries in a rectangle on the top left corner of the cheesecake to represent the stripes of the flag. Place blueberries in the top left corner to create the stars.

Refrigerate the cheesecake for at least 4 hours, or until set. For best results, chill overnight.

Slice into squares and serve chilled.