Fun fact: Trains in America run slower today than they did in the 1920s. One reason for this is because of government weight regulations on train cars that make them slower.
That being said, China is in an infrastructure bubble right now. That's why there are vacant cities*. Debt spending on infrastructure like railroads and entire cities makes up a larger part of the Chinese economy than the American economy.
Europe's far higher population density than America might explain why there are more transport railroads there. Europe has around 111.739 people per square kilometer, whereas the US has around 33.27 people per square kilometer.
Despite its history and lack of high speed rail, I think the system in America right now is pretty decent. America has the most miles of railroad out of any country in the world*. There are lots of railroads in use in America today, just not high speed ones. Railroad companies here simply make more money by shipping hundreds of transport containers on one train at a slow speed, than by shipping a small amount of passenger carriages at a high speed.
* https://www.businessinsider.com/pictures-chinese-ghost-cities-2010-12?slop=1#heres-chinas-biggest-ghost-city-zhengzhou-new-district-4
* https://en.wikipedia.org/wiki/List_of_countries_by_rail_transport_network_size#cite_note-3