I'm not aware of there ever having been a July 4th story contest here. Lit.'s Summer contest doesn't come until summer is almost over in the Northern Hemisphere.
I've always shied away from Independence Day stories in the Summer Lovin' contest because the actual day was long past before the contest starts, but I doubt the readership would actually ding you for it. It's most certainly on theme for that contest.
I’ve never heard of a July 4 contest either and I’ve been a reader or more here since the site got started. But yeah, do a Summer Loving story about the 4th if you want, it qualifies for sure.
Well, I'm writing an Australia Day story for Summer Lovin', which is in January. The date isn't important, it's about the sun, outdoor activities, and cold beer.
The Nude Day contest (July 14th) would be more appropriate for an Independence Day story than Summer Lovin', and that contest is open now. You have until July 5th to submit your story.
My Nude Day story for last year's contest took place over the 4th of July Weekend, but "Nude Day" (not really much of a thing) is the same date as the French National Holiday, so I've also put Bastille Day stories in the Nude Day contest.