There are quite a few good blog posts out there about why we should celebrate what we are celebrating today, and even a thoughtful one about whether we should be celebrating at all.
I'm proud to be an American, and I do love this country, though I sometimes worry quite a bit about the direction we are heading. I don't see any real contradiction in this, as many ancient patriots of many different nations were among the first to sound the alarms about the death and decline of their own nations or empires. Those who love a country are often quite realistic about her flaws, and can praise the good while acknowledging the bad; jingoism or overdrawn nationalism are often more self-serving than real patriotism.
Our country was founded on principles of liberty, and it is on those principles that it will stand or fall. But we've become confused in recent times between liberty and license, between the freedom to do whatever is just, and right, and good, and the freedom to do whatever we wish, regardless of the consequences to those around us.
Liberty is properly ordered first toward God, then toward family, and then toward country; liberty seeks the path of righteousness and avoids evil, freely choosing good. But license is ordered first, last, and always toward the self: provided the self is free to choose whatever of pleasure or hedonism it seeks, God is degraded to mere "spirituality" which is only an emotional exercise in the game of creating good feelings about whatever one desires; family is redefined to mean whatever group of related or unrelated people one surrounds oneself with, with whom one is randomly likely to share sexual favors on the grounds that those are worthless, but avoid sharing one's stuff, on the grounds that that is priceless and irreplaceable; and country means primarily the courts, by whose instrumentality one hopes to reshape society and coerce it to approve of whatever depths of depravity one wishes to define as both normal and a fundamental right which one should always be free to enjoy, and to force others to accept.
Liberty and license are concepts which are not related to each other; rather, they are opposed at the deepest level. True freedom is always the freedom to do what is right and just, not to define as right and just whatever it is that one desires to do.
And in recent times our nation has had that exactly backwards: what is natural and ordered towards goodness is deemed too narrow, too prejudicial, too extreme to have anything to say to our modern society, while disorders of every sort are upheld as good things, as the sort of things that are right and proper to man.
So it is that our society first approved contraception, and now all but mandates it; approved abortion, and still fights against the repulsion most ordinary good people instinctively feel towards the whole concept; has begun to approve gay marriage, and wishes to stifle and silence the voices which are raised against it; approves divorce and serial marriage, and sees as abnormal those few religions which still oppose it--and on and on. An admirable bent toward liberty has been reshaped into the most twisted form of licentiousness imaginable, and our society continues to approve it all, as if the price of liberty is not sacrifice, but the embrace of perversion in whatever form it presents itself.
Our founding fathers would, for the most part, have had no trouble condemning all of our society's various immoralities and wickedness, because most of our founding fathers understood that the principle of liberty does not operate at all in a moral vacuum, when freedom to do what is right becomes freedom to do anything at all. If our liberty is not based in a proper understanding of man and his place in the universe, then it is not liberty--it is, or will shortly become, the worst sort of tyranny: the tyranny of profligacy, where the only things condemned are those which in their innate goodness illustrate clearly the multiplicity of evil that surrounds them.