When they get the number of stations into the tens of thousands then I'll concede the point.
I don't think the number needs to be anywhere near that high. Not remotely.
Don't make the mistake of thinking of supercharger stations as analogous to your average neighborhood gas station. They're nothing like that. Supercharger stations are only needed for long-distance travel. They're analogous to the big travel centers you find along the interstates and other highways which carry significant amounts of long-distance traffic, and the numbers required are similar to those of travel centers. If there's one every hundred miles or so along every long-distance travel corridor (which in the US is mostly just the interstates, though there are a few areas with long-distance highways) then coverage will be complete.
With electric vehicles, 95+% of charging is done at places where vehicles spend lots of time parked, primarily homes and workplaces. Such charging doesn't need to be particularly fast. Fast charging only matters when you're driving distances beyond the range of your battery.
You mention North Dakota, for example. Move the slider on that map to 2015 and you'll see they plan to put three superchargers there. That will cover the long-distance travel across ND, and most long-distance travel within ND. Add another supercharger on highway 2, midway between Grand Forks and Minot and you'll have covered nearly all of the rest. Add four of five more and you'll be able to get to any destination in the state without worry.