People only using aggregate density calculation is so overly simplistic. Inside of each country there are patterns.

Imagine a country with two huge cities and a very long empty desert in the middle. Density can be low but its still easy to connect.

I not totally skeptical that some places are harder to connect then others but given we live in the modern world with algorithms and satellites we should be able to do a better job than top level density.

And I'm not saying this to convince you that Switzerland is easier. Frankly I do think it easier. But because I am actually interested if anybody knows if such work and estimations exist.

Like lets assume all fiber, cable and old phone connections are gone. How hard much would it cost to get every person to some very high speed.