actually, the US experienced maturity, responsibility, and a social conscience briefly, around the time of WWII, and has since lapsed into decadence, characterized by long periods of narcissistic oblivion, punctuated by brief moments of horrified self-awareness and occasional diversions into fear-driven aggression.
this is best exemplified by the Baby Boom generation, most of whom refused to reach psychological adulthood, and basically have remained at the maturity level of a 17-year-old boy well into their 50s. of course, now, with their depleted savings and retirement funds, foreclosed houses, offshored jobs, failing Social Security, and privatized Medicare, they wonder how they managed to piss the country away on shopping, wars and tax cuts.
behold the Roman Empire redux, in fast-forward, complete with a mad Emperor, a deadlocked legislature, and a corrupt judiciary. the Huns and Goths are due any minute.