But the density in the US is not _that_ different. Sure if you take the average over the whole country or states like Texas or Arizona then you end up with numbers. But the north east of the US is comparably densely populated to Western Europe. And even parts of California/the west coast are similarly densely populated. Albeit with larger separations between population centers. Which, as a German, does not sound so bad, given that our high-speed rail has to stop every 30mins because the next city just isn’t that far away.
Really it is a (maybe unintentional) decision not to use trains for passenger rail.
On the other hand. The density of population (and thereby logistic) centers in Western and Central Europe makes freight trains much less useful. From Germany you can reach all of Europe in basically 2 days. And that’s already stretching what you’ll need to reach in practice. And then you add the expense of getting the load to a train station and away from it again and you basically never end up with an easy or obvious advantage for the rail system. What you see here quite often is that a single company/factory fills up a whole train (think car carrier or chemical transport). In these cases at least one end of the journey is typically directly linked to the rail system and the other end is probably a port. And that’s before you take into account that a useful expansion of the rail system requires coordination between multiple governments (there was/is a plan to link Rotterdam to Venice by high volume train connections. AFAIK this is still limited by a lack of expansion of a short part in northern Germany)
So yes. There is a bias towards passenger rail, both for operational (passenger rail is much faster to accelerate/decelerate) and political (passengers sometimes punish politicians for delays, freight doesn’t) reasons. But even without that. The geography and industrial makeup doesn’t produce the same kind of advantages as in the US. So it would still be used less
