I read a lot of things with unreliable narrators or explanations, so i say that stuff like magic shouldnt be trusted to highly.
Maybe magic is only Icelandic belief magic or Finn nature magic, maybe there is native american shamanism or atheist science magic, maybe there isnt magic at all, for all we know magicians never did anything showey, so its best not to tackle that issue beyond cultural stuff.
Eygeptian gods arent as known as Nord gods, and werent worshipped for longer than norse gods have been, plus Islam is too strong there. The biggest thing is soem sort of combination of Islam and eyeptian gods, replacing stuff in the Quran with "The Nile" and other eygptian gods, maybe some greek ones.
That is, if they manage to survive the plague at all, which given all the clues to when the comic starts, doesnt give too much hope to the poor eygptians, but with enough dramatic interventions any country can survive, and if humans turn out not to be as monstrous as the trolls, maybe a pan-nile nation can emerge. (Hippo beasts though, that cant be pleasent, maybe the crocs can fend them off)
Brittania: Well maybe there is a community but it didnt breach waters yet. Either the United Kingdom became more closely tied, with maybe Ireland re-joining, or they scattered to be on their own, with England, Scotland, Wales and Ireland. Personaly i prefer the first because its nice when people get along. "Rule Brittania, Rule the waves"
To coin a term: Dramatic Intervention: Corrupt politicans? Incompetant leaders? Religious nuts and idiotic bigots? What are those? The governorments make ONLY good decisions, and maybe some bad ones, as long as the country survives the rash illness. Of course this cant happen because all of the above exist and are likely to hamper all the good people, but maybe that can make a very-likely-to-survive-country a survived-by-the-skin-of-its-teeth country.
For short: Any country can survive if you belive hard enough.
Also @Raya the thing i didnt like about this line was "Only Nordics can into immunity" which carries a lot of very unfortunate meanings to it.
In other news: I saw a mod for Crusader Kings that is set in US 2666AC, after an apocalypse punched everything back to medival age and caused a drastic change in beliefs, The Founding Fathers and The Atom became as holy as Jesus and The New York Giants and other sports teams are famous mercenries. I couldnt find the mod afterwards, but i think that toning it down can create the culture in the US at year 90.
Food for thought:
Africa: The Maghreb, the center and South, what will go with those?
Malta: One of the oldest human settlements in history, dating to beyond the stone age. Will the legacy stop with Illness? how will they be like if they survive?