I think you're reading too much into this, or possibly over thinking it. People aren't celebrating what you claim they are. Sure, a small minority is, but I don't think you're talking about them.

Flags are the Christmas tree of the 4th of July
Fireworks are the trick or treat candy of the 4th of July.

People are enjoying a long weekend in the summer, that's about it. Everything else is just theater dressing.