For those that have some trauma that the fireworks will trigger, try a Guided meditation by Belleruth Naparstek called, "Healing Trauma". (HealthJourneys)
Receiving Reiki sessions can also help to reduce your anxiety, bringing in calm to you. Thus, you start to learn how to calm yourself when you are triggered.
I hope this can help. Happy Fourth of July! Cheers to Freedom. -Cynthia.