The onset of America’s 250th birthday should feel like a greater deal than it is.It should be, in the words of John Adams, “solemnized with Pomp and Parade, with Shews, Games, Sports, Guns, Bells, Bonfires and Illuminations from one End of this Continent to the other from this Time forward forever more.”Despite this moment, when Americans are largely feeling down about themselves, the world lately has found itself quite impressed by America.And …