The spirit is alive
These words are not the most-often-cited part of the Declaration, but they are the core of it. The legitimacy of a government comes not from force, not from God, not from royal succession, but from the consent of the people it governs. There would have been little point in establishing the United States as an independent nation if it had been just another monarchy or theocracy. It's the principle that the people determine the government and not vice-versa that was important.
The United States in practice fell far short of its ideals until much later. One-eighth of our people were enslaved until 1865; one-half were disenfranchised until 1920. The fight to preserve and expand freedom in other areas continued, and continues today. But the ideals have always been there, calling us in the right direction.
On these anniversaries, distracted by mall sales and fireworks, we modern Americans too easily neglect to keep those ideals in our thoughts. Yet they have thrived and spread -- even, as we have so recently been reminded, to the far side of the world.