Mostly because the one-third of colonists who fought to shrug off the shackles of tyranny that bound the colonies to Britain managed to get France to come into the war against the British. Thus the colonies became free to spread out across the continent and steal land from its rightful owners.
If they had lost, July 4th would be the North American equivalent of Guy Fawkes Day, which celebrates the foiling of the Gunpowder Plot to blow up parliament. Which only goes to show that a successful revolutionary is a patriot and a successful guerilla is a freedom fighter and not a terrorist.
Of course, by the convoluted course of history, this new nation actually did become a beacon of freedom—originally for white men of property, later for the huddled masses yearning to breathe free and more recently for educated persons of color.
The bloodiest war in American history was the Civil War, which was fought to prevent Northern industrial values from undermining Southern slave culture and was eventually won by those who wished to preserve the Union at any cost. Further blood was shed to conquer Mexican territory, ethnically cleanse any land of value of pesky Native Americans, free Cuba and the Philippines from corrupt Catholic Spanish rule and replace it by Protestant American rule, indirect or direct. And to save Asian nations from governments inimical to U.S. Foreign policy.
Fittingly, we celebrate the Declaration of American Independence with fireworks, concerts, parades and outdoor barbeques, clam bakes and picnics. As well as by shopping for discounts. What could better express the intentions of our Founding Fathers who opposed paying taxes and tariffs to support the preservation and expansion of the British Empire in North America?
The irony is that most of us alive in America today have good reason to cheer the Declaration of Independence and the county which grew by stumbling steps from that beginning. We live in a prosperous nation which allowed immigrants and their descendants to flourish with a minimum of tyranny and an unprecedented abundance of individual liberty and economic opportunity.
Chances are that few of my family would be alive today if the United States hadn't provided our ancestors with shelter from Europe's virulent antisemitism. Likewise it provided hundreds of thousands of Irish immigrants with shelter from famine, oppression and poverty, to say nothing of those fleeing persecution, revolution, violence and poverty from every corner of the earth.
So our hearts do swell with pride and gratitude toward those bewigged, Anglophone gentlemen who proclaimed our independence 234 long, bloody years ago.
That this country became the greatest military and financial power on the globe may or may not be a good thing. That it granted so many displaced and despised and simply ambitious people a home where they could enjoy the blessings of freedom, education and prosperity is a nearly miraculous achievement in which we can glory.