I'm really sorry if the subject has already been approached, but what about South America? I've been thinking about it, and I think most of the countries would be really devastated, given the tropical climate and the extensive fauna, but there could be a few isolated communities.
In Brazil, for example, there are two arid areas that have almost no vegetation (mostly in the central and northeast regions), like deserts, with little place for trolls to hide and make nests. If the communities there could find a way to survive the first decades, they could hunt and exterminate the trolls quickly (and here I'm thinking about desert scouts and troll hunters, and getting really excited
).
In Patagônia (at the extreme south of South America), we have an extremely cold area, where communites could survive similarly to the nordic ones.
I'm just wondering about it. Maybe you guys will shot down my theories with your science in a second, I don't know.