So it's very expensive to overfly the US without landing, and once you land you can't avoid immigration even if you are just transiting on your way to another country.
The overland fee is $61.75 per 100 nautical miles (and it's a lower $26.51 per 100 nautical miles)[1]. Is this really that high? Let's say a flight from Canada to Mexico has to cross 1600 nautical miles overland the US. That would cost 16 x 61.75 = $988. Isn't that pretty low? On a flight with 200 passengers, that's an extra $5 per passenger.
[1] https://www.faa.gov/air_traffic/international_aviation/overf...
