Infuse the vodka with the flowers for about 10 minutes; you'll see the liquid turn dark blue. Set aside 1 1/2 ounces for the drink—the extra vodka will keep!
In a highball add the jam, cherry herring, lime and bitters. Fill with crushed ice and layer in the soda water by pouring it gently. Finish with a layer of infused vodka on top. Garnish with a mini American flag (if you like!) and a straw.