Americans celebrating our 245th birthday this weekend largely fall into two groups. Those in the first will simply take it for granted that freedom rings—assume that the liberties we’ve traditionally enjoyed are liberties we will always enjoy—turn on the ball game, hit the pool, and look for the fireworks. That’s a choice most Americans will happily make.Those in the second group will do something many of us do when we hit one of our own personal milestone birthdays—30, 40, 50, etc. We can pause, if only for a moment or two, to assess where we are, and where we’re going.Things...