@vimothy you said a lot of things and I'm not gonna go through them all one by one or anything. tho generally I'm pretty bewildered by some of your main themes. for one, your bizarre insistence on a single axis political spectrum that is so clearly - even by your own examples - inadequate. or how an economics grad student of all people can make talk about the immateriality of economic issues (and beliefs) to where the political center is. that said:
obviously the U.S. is on most (definitely not all) issues and in general more socially liberal, to varying degree, than it was in 1962 or 1912. just as obviously, the last 40+ years has seen a rightward rollback on the economic side of social policy (inequality and disparity, social safety nets, etc), in financial deregulation and especially in labor relations (examples too numerous to mention). in fact, it's just as easy to see the last century as a gradual destruction/defanging of the traditional Left - first the radicals crushed during and post-WWI, then the New Deal (which was bitterly criticized by a segment of leftists at the time, and then again in retrospect by the New Left), then the Great Society (a watered-down New Deal), eventually Clinton and now Obama, a center-right technocrat who a big chunk of the country thinks is a "socialist". that such a narrative would be just as selective and imperfect as yours just speaks to the problem of creating sweeping historical arcs in the first place. anyone with the training can use it to construct any narrative they want primary sources and/or raw data as the case may be.
as far as the rest...I mean eh. the timeframe for this radical break is totally arbitrary, I could pick a dozen other points and argue the exact same thing just using a word other than rationalism (or I could just argue that year zero moments don't happen that way at all) and eudaimonia and all this...well I mean droid said it already. it is interesting to see you choose a Platonist definition of modernity since that fits into my Edmund Burke picture of you these days (albeit an Edmund Burke into black metal and whatever).
but anyway, this all got pretty far afield.