Historians have noted that, by the time the Bastille was destroyed, there were only a few prisoners left. But the storming of the Bastille is more important than simply trashing a nearly empty building. The Bastille symbolized the arbitrary power of the king, in the same way that the Star Chamber symbolized the arbitrary power of the English monarchy. And if you don't think that the United States has similar symbols, I would refer you to the Third Amendment to the Constitution, which prohibits the billeting of soldiers in our homes except in time of war.
Why on Earth, you ask, would the Founding Fathers waste a whole Amendment on that? Let us turn back to the period prior to the Revolution. Soldiers were regularly quartered in people's homes. They came, they took over, they stayed more than the three days when fish and house guests begin to stink. Most often, they were pretty well-behaved, but every so often you'd get a group that raided the liquor, got drunk, used the furniture as firewood, killed the cow and cooked it up for supper, and then tried to do the daughter of the house. This, understandably, made people mad. More importantly, it symbolized the arbitrary power of the British government. See, the French didn't like that, the English didn't like it, and neither did we.
Just as a note, neither did the Cubans. When the Cuban Revolution was a scant few days old, the population of Havana went out and systematically knocked down every parking meter in the city. Why? Well, not a single centavo from any of those parking meters had ever made it into the government coffers. Not one. Not ever. A symbolic act, just like, uh, the Third Amendment.
And J reminded me that a holiday requires music.