Some of us are better informed. And a large number of us have the perspective of comparison, aware of America's faults, but unimpressed by claims that it is not perfect: we compare and decide that "America is the greatest, freest and most decent society in existence. It is an oasis of goodness in a desert of cynicism and barbarism. This country, once an experiment unique in the world, is now the last best hope for the world."
Why are we patriotic? Because it's the right thing to do. Does that mean that we are uninvolved in politics, we don't try to make things even better? No. But, and here's the rub: you always want who and what you love to be better than they are right now: and those of us who raise children have the pleasure of seeing some of that happen and the practice to keep it up.