I'm also Norwegian and got a very similar map, though with more emphasis on a New York dialect. I'm guessing it has to do with our English being heavily influenced by popular media, in which the midwest might have less vocal presence.

This is so weird, how is it even possible to talk like a New Yorker, Californian, and Floridian all at once?! No Americans got anything close to this.

apparently norwegians are just more american than swedes in general