1) The Bad Stripe (West Virgina, Kentucky and Tennessee, Missouri, Arkansas, and Oklahoma) is evident as a negative outlier as usual. These make up 6 of the bottom 11. For fans of Albion's Seed, this is where the Reavers are, i.e. Greater Appalachia. This also shows the limitation of a state-level analysis. There is significant structure within the states. Pennsylvania's southwest if taken separately would very likely look like West Virginia. The southeast if taken separately would be much more like New York and New Jersey. Same thing for Missouri - the northern part of the state is likely more like the Upper Midwest, and the southern part is the Ozarks, part of the Bad Stripe and more like Arkansas.
2) The Upper Midwest and Utah stand out as positive outliers, as usual. Moynihan's Law - is it the result of Yankee settlers (again Albion's Seed), non-British Isles North European immigrants, or some combination? (Map below from Wiki on German Ancestry in the USA and Canada.)
3) Very interesting that two demographically similar states like the Carolinas could be so different in this rating. North Carolina has done better economically than South Carolina, and culturally does tend to move in sync with Virgina (perhaps most famously in the 2008 presidential election predicted by Nate Silver) - which makes sense because South Carolina was largely settled from Georgia initially, and North Carolina from Virginia. Still, they're not THAT different, and they have a very different happiness outcome.
4) I can't argue for similar historical links to the Reavers for Mississippi, Alabama and Louisiana, who as always fare very poorly. You'll have to develop your own theory for that!