That's one every 5750 (ish) square miles.
Did you seriously just divide Earth's total land area by the number of chargers? Great to know that I can pop over to a Tesla supercharger when I'm in the middle of Antarctica, Greenland or the Sahara.
Tesla Superchargers are only found in:
* The US (not including Alaska)
* Southern Canada (and not all of southern Canada)
* Southeast coastal Australia (plus one in the west, and a couple in NZ)
* South Korea
* East China
In the US, Superchargers are spaced 50-100 miles apart along all but a handful of interstates (the latter to be added by the expansion), as well as smaller highways in more densely populated areas (many more to be added by the coming expansion). Which is more than enough to drive cross country. Note that we're only talking about superchargers; there are also many more slower chargers in place.
Comparing it to gas stations is a stupid comparison, firstly because there are vastly more cars on the road, and thus vastly more gas stations needed. But beyond that is the more basic point: EVs don't do most of their charging at superchargers. Gas vehicles must fill up at gas stations. EVs overwhelmingly don't fill up at superchargers. Superchargers are for trips.