Image proof then.
As you can see by the picture I've just posted, there are two main rivers, and, get this, look at the stuff at the top, left and right sides of the image. MOUNTAINS. Closer to Isshu than New York City, I think. Also, you might notice there's a funny blue splot thing in the middle of the map. That's Prospect Reservoir, in the exact same place as Pokeball Lake in Isshu. I'll admit, the shape of the area between the Parramatta and Georges Rivers is shaped a bit more like a hammer than a rectangle, but the area's shape is
always altered when turned into a Pokemon region.
So, how's it with the evidence for Sydney = Isshu? New York has the shape, Shanghai has the city size and landmarks, Sydney has the topography. I've absolutely no idea where that Nunavut argument came from.
I was only kidding around at first, when I said Sydney, but now, I'm quite serious. You could say that I've been convinced by my own evidence.
So, how many is that now? New York, Shanghai, Hiroshima, Sydney, Nunavat.