Not sure about the analog dash clusters, but the digital dash clusters had different gears in the odometers for the imports.
http://www.installationinstructions.com/FYI/odometer FYI.pdf
They were calibrated in KM. When you think about it, if you rack up mileage on your car, the analog odometer is calibrated in miles. But if you look at KM, it'd show around 20% less than the actual mileage, since KM should show around 100 every 62 miles.
So, if your analog dash is shown in KM along with MPH, the big question would be whether the mechanical odometer is set up for KM or MPH.
With that thought, if you were to purchase a low mile GN from a Canadian seller and it showed 10,000 miles on the clock, it would actually be around 6200 *miles*.
Conversely, if you lived in Canada, and purchased a GN from the states that had, say, 50,000 miles on the clock, it would actually have about 80,500 KM on the car.
This is all assuming the import cars use the same internals on the odometer.
Now, back to the OP, it poses a good question about the difference between the imports and the US cars. Since the KM is shown on the face of the "blank center" boost screening, it would be a fair assumption that the odometer gears are different. It would take some inspection to determine if that's a fact. And if it is, then there are at least several GN's where the mileage shown is inaccurate.
