The difference is because in America, there's 2(3) countries. In Europe, you travel between ~10 countries. The budget/mentality is different since you operate in international level with international import/exports.
Not sure why anyone would make excuses for the US on trains. There are some great opportunities to get it right. Or ignore it and wait for automated bus services.
Specific through services make it easier a few routes, such as the CityNightLine sleeper services, since there is one train and one operator for the whole route.
That's the problem with N. America, airplanes are cheaper for our geographic situation. Because routes are not set in stone, they can be changed as the demand adjusts itself.
When you lay out train track, you can't change your mind in 20 years or you need to change your infrastructure.
Not much more than across US states. https://en.wikipedia.org/wiki/Schengen_Agreement
(although as someone else commented, it's not easy to get trains going through more than one border).
> Or ignore it and wait for automated bus services.
Buses won't reach 330 km/h (210 mph, speed of trains made in my country, Spain).
It is an economical calamity, for a country already in a deep crisis, that the taxpayers will have to pay during decades.
The AVE is an example of how infrastructures should never be planned and deployed.
My point, though, was about the trains that are made in my country, not how they make use of them.