I suspect what is going on is just a matter of relative density. I'm not sure what you mean exactly by "central EU," but just guessing from a map I get Romania as the least population dense country that I would think of as Central Europe at 83 / km3. That is more than double the US pop density and if it were a US state only 15 out of 50 would be more dense. So then taking the least population dense region of the least dense country I get Tulcea with 23 / km3. That's 66% of the density of the US (37) which would come in at 34 / 50 if it were a US state.

So the most sparsely populated region of the most sparsely populated country in Central Europe is just a bit below average for the US. Our least dense state is Alaska at 0.5 / km3 or almost 50x less dense than that. But that's almost cheating. So lets take mainland only and that's Wyoming, with 2.3, so 10x less densely populated than the outlier in Central Europe.

So basically the US is just really damn empty to the point there just isn't any comparison in Central Europe and that's why it's so hard to get internet access out there.