The answer comes, like so much else, from the ideas of Ayn Rand. For America is not a nation in the classical sense of nationhood: there is no common culture (Hollywood is only in California), there is no kind or dictator who binds the people together. There are huge divisions - on race, on political affiliations, even on geography (ask a New Yorker to live in Alabama). But what keeps the country together is an underlying logic - the logic that the individual matters, that the pursuit of happiness is a fundamental right of each individual. It is this idea, this respect for the individual that keeps this country together.
Of course, that does not mean that America lives up to its own ideal. This month, a new law in Illinois comes into force, requiring waiters to be licensed. If you thought capitalism means the end of a government license-raj, Illinois is certainly proving it wrong. This state has so many mindless laws, pointless licenses and complex laws that it is really no surprise that The Economist rated it as one of the worst states in this country for small businesses, which have to bare the brunt of these laws more than anyone else. On foreign policy, America is beating a hasty retreat from Afghanistan and has given up on trying to compete with China for leadership of the future. No, America is not living up to its ideals. But that is why you Independence Day matters - for in a democracy, once people realize that there is a problem, they can fix it. It's a question of thinking about it.