1. Preheat oven to 325°F. Line a 9-by-13-inch baking pan with foil, leaving a 2-inch overhang on 2 sides. Mist foil with cooking spray.
2. Make crust: Pulse graham crackers in a food processor until finely chopped. Add sugar and salt, and process until well combined. Add butter and pulse just until mixture begins to come together; it should not form a ball. Press mixture evenly over bottom of prepared pan. Bake for 25 minutes, or until set. Let cool on a wire rack.
3. Make filling: With an electric mixer on medium-high speed, beat cream cheese and sugar until smooth. Scrape down sides of bowl. Reduce speed to medium-low and add eggs and egg whites, one at a time, beating until just combined. Beat in lemon juice, vanilla and salt.
4. Spread cream cheese mixture evenly over crust. Tap pan on countertop 3 or 4 times to burst air bubbles in filling. Place pan on a large roasting pan and put in oven. Pour hot tap water into roasting pan until it comes up about an inch around baking pan. Bake for 40 minutes, or until filling is just set. Cool completely on a wire rack, then cover with foil and refrigerate for at least 6 hours or overnight.
5. Use foil overhang to lift cheesecake out of pan and onto cutting board. Heat a large sharp knife under hot water; dry knife. Trim off edges of cheesecake. Carefully cut into 24 bars, rinsing knife under hot water and drying thoroughly between each cut.
6. Transfer bars to a serving platter. Decorate each bar with blueberries in upper left corner to resemble stars on the American flag. Place jelly in a ziplock bag, seal bag and snip off about 1/6 inch at one bottom corner. Pipe jelly in thin lines on each bar to resemble stripes on flag. Or decorate with a variety of fresh berries. Serve immediately, or keep covered in the refrigerator for up to 3 days and decorate before serving.