Doomsday plus 33

33 years have passed since colonel Petrov wasn't at the right place at the right time, and the bombs flew. North America was devastated, with US populations bottoming out as low as ten percent of pre-war levels, but have since the late 1980s been growing again (at least in part due to the rather primitive nature of contraception available in most of North America). There are now some 7-8 million people inhabiting former Canada and 37-38 million inhabiting the former US (with its vast open spaces and fewer strategic targets, Canada suffered less overall depopulation). A "southern hemisphere consensus", led by South America, Australia-NZ and other southern nations lightly hit in the war, has emerged as the principal driver of global politics and economics, and the New League of Nations has replaced the old UN. 

North America is slowly stitching itself back together, and the old USA, for long merely a memory in much of the continent, seems to be returning. Organized states replace warlords and "emergency regimes", ingenious low-tech or alternate tech fixes to local resource crises are driving something of an tech boomlet, and North America is increasingly reintegrating into the global economy. The radiation has mostly died down, even in the vicinity of smashed nuclear reactors [1]. Much of the country remains depopulated due to people moving from more chaotic to more ordered areas, fleeing fallout or bandits and warlords, and isolation due to local roads and rails disintegrating in the weather due to neglect from regional governments too overburdened to carry out extensive maintenance. A combination of fear of fallout and angry declarations of territorial integrity on the part of even the tiniest survivor communities has largely limited foreign intrusions to the occasional port or offshore island, although of late the League of Nations has taken on a more active role in helping local north American states restore order and patrol their coasts. 

The jokingly called "Kentucky-Wyoming axis" is moving towards a US unifying once again lands west and east of the Mississippi, and to squash the remaining warlord states and wilderness crazies. Navigation on the Mississippi between Louisiana and Kentucky is now fairly safe (aside from the dead trees: the corp of engineers isn't quite as well funded as it used to be) and with the Lawrence Raiders trying to keep their heads down, travel between the Atlantic and the Great Lakes is likewise no longer something requiring an armed floatilla. Of course, what with the massive trauma and years of isolation, some bits of the former US and Canada have gone a bit gonzo and may take a while to reintegrate...

[1] See the flourishing wildlife of the Chernobyl exclusion zone. Sure, I wouldn't live there myself, but north American beggars can't be choosers.