We cruised july 4th on the Wonder this year. Fireworks were on that night and they were a little more extravagant than I had remembered from previous cruises. They did have a special "All American Menu" that night in addition to the regular menu. We were told to keep the menu as a souvenier and it was quite nice with pictures of mickey etc. dressed in his red, white and blue.
There was also a special show on deck that day, with characters and songs and streamers I think. It was fun and the cast members all made it special by wishing us a happy fourth all day long. The ship was also decorated that day with flags and red, white blue decorations. There was also a balloon drop in the atrium.