Being old has its advantages: The A.A.R.P. discount, the wisdom of years, not having to care a whit where Taylor Swift gets married. For America, born when nickels had bumblebees on ‘em and 117 years old this year, it means we don’t just have to look 25 or 50 years back to see how the nation viewed its national holiday. We’re well-seasoned enough that on this, our nation’s semiquincentennial, we c...