Eurorail was able to straighten their rail alignments in Europe as it was built, and had a legacy of having straighter alignments than we have here in the US, as its a denser continent with more political capital to spend to eminent domain buildings over a longer period of time to get that trackage dead straight.

Rail management in Europe is also not the greatest, they tried to separate rolling stock (the cars you ride on) from the company that owns the rails, while forcing them to sublease track rights, which has created a mess as of late.

Due to topographical issues, short of another FDR style project we will not see something similar in the US in our lifetime.