Other than a few minor communities in coastal Louisiana and Maine/New Brunswick nothing effectively survived east the Mississippi in the US. Except for cannibals and the 'Nantucket Anamoly'.
cue eerie music
Prince Edward Island was the only major Canadian population center to survive east of the Mississippi. Nova Scotia and Newfoundland were wiped out, based on Stirling's estimate of the local (lack of)ability to feed themselves.
Makes sense though too. Halifax is a major city not on the scale of say Toronto or Vancouver. And it is on a island. And I doubt that much of the fishing fleet is sail or oar powered. Which kinda sucks if the folks on Newfoundland and Nova Scotia had some wind powered boats they might have survived, albeit barely. Both St. John's and Halifax have major airports so any planeloads of people mean more mouths to feed. Still with just a little more food or a few less mouths too feed both of those places would have made it.
which isn't necessarily correct but that's canon in his books
Apparently Sardinia and Corsica did not survive, Sicily DID survive but Stirling hinted broadly that something was going on which was less than pleasant to explain why Sicily made it.
Northern Scandinavia came through and by Change Year 10 a union of the surviving Scandinavians known as Scandia has formed, added 60-70K Icelanders to their own 250K+ survivors and arranged for (former) Germany to be added to their holdings with the English.
The Southwest including Tucson became an unrivalled dead zone because the water supply was lost when the Hoover Dam and associated projects failed almost instantly.
You can access the opening chapters to the first six books in the series at this website, along with much else:
http://web.telia.com/~u54504162/scifi/index.htm