Line an 8x8-inch baking pan with parchment paper, leaving some overhang for easy lifting.

In a medium bowl, combine the graham cracker crumbs, melted butter, and granulated sugar until the mixture resembles damp sand.

Press the crust mixture firmly and evenly into the bottom of the prepared pan. Place in the refrigerator to chill while you make the filling.

In a large mixing bowl, beat the softened cream cheese until smooth and fluffy.

Add the powdered sugar and vanilla extract, then mix until fully combined and creamy.

In a separate bowl, whip the cold heavy cream until stiff peaks form.

Gently fold the whipped cream into the cream cheese mixture until smooth and well blended.

Spread the cheesecake filling evenly over the chilled crust and smooth the top with a spatula.

Arrange the blueberries in the upper left corner of the bars to create the blue field of the flag.

Place the sliced strawberries in horizontal rows across the remaining surface to resemble the red stripes of the flag, leaving thin gaps of cheesecake showing between rows if desired.

If using, drizzle a small amount of warmed jam lightly over the strawberry rows for extra shine and flavor.

Refrigerate the bars for at least 4 hours, or until fully set.

Lift the cheesecake from the pan using the parchment overhang, slice into bars, and serve chilled.