Well, first, this is Harper's Weekly, not the New York Times.
Harper's was published from 1857 until 1916 by which time it was a strong supporter of Southern Democrat President Woodrow Wilson.
Second, the editorial's argument for "centralization" here is neither profound nor controversial, it simply notes that throughout history countries united under one government prosper peacefully far more than when divided into many tiny & warring principalities.
It cites the examples of Germany, Italy, France and England which prospered when united, were weak & warring when divided.
And, this particular editorial makes no efforts to discuss the uniqueness of the American experiment in federal government, of states united voluntarily by a democratically ratified Constitution, or of the constitutional problems represented by unilateral, unapproved declarations of secession at pleasure.
But we have, and will, as needed.
Americans don't have the experience of being divided up into smaller countries that are easily dominated by foreign powers, so we tend to underestimate the value of national unity.
But there are two sides to the question. Divided Italy and Germany easily fell under the rule of foreign powers -- France, and in Italy's case also Austria and Spain -- but arguably their greatest cultural moments came when they were still divided into smaller countries. That's certainly true of Italy.
To be fair, though, Harper's couldn't see what the 20th century had in store for Germany and Italy after unification.