I don't buy it thought. I think the reason why the spend is less in Europe is due to higher salary equality - good people take job in government because the salary is only 50% higher in private sector (for tech, even less for other areas).
The areas where the vast majority of Americans actually live are fairly high density.
Some cost might come down to density, but not much.
Arguable, Denmark has a super low density also if you count in Greenland.
As also written, I don't buy that argument. I think the core is inequality.
If we're considering contiguous US, then no.
Europe is 3.93 million square miles.
Contiguous US is 3.15 million square miles.
As a non-contiguous later addition, with a small population, where statistically nobody lives there per sq mile, and is not pertinent to the discussion of population density as related to infrastructure problems?
Except in what's holding US bureucratic efficiency down (what we were discussing), and requires spending inflated federal budgets for little returns, Alaska is a big factor relative to its size...