Interesting to see someone already got 100 *Gb* Internet. It makes you very lucky but a bad example, though. <G> I too know people who live in places which were used as "technology demonstration" and got very advanced connections (not 100Gb, though), just, they don't represent the average citizen.
The 3% referred to "Census blocks with housing units" - not the whole "land area", and "with housing units" I guess it excluded blocks with "zero population".
Deploying a new network infrastructure may have different challenges, depending on how the population is "dispersed". Cabling a few large cities is cheaper than having to cable a lot of small towns. Some European countries population is far less concentrated, requiring a far more distributed network - with the need to reach even small mountain towns.
It is true some rural areas may be "hundred of kilometers" (a Yankee using metric units!!?? Maybe a fake Russian post??? LOL!) from a large cities, but you don't really need to bring a fiber cable directly from NY or SF... any smaller nearby city will be enough.