If there’s a single word that best describes the rating agency’s decision to downgrade America, it’s chutzpah — traditionally defined by the example of the young man who kills his parents, then pleads for mercy because he’s an orphan. America’s large budget deficit is, after all, primarily the result of the economic slump that followed the 2008 financial crisis. And S.& P., along with its sister rating agencies, played a major role in causing that crisis, by giving AAA ratings to mortgage-backed assets that have since turned into toxic waste.