There is no excuse for the US’s failure. Many countries have large areas to cover. China is a similar size and has massive HSR coverage. The US could too if they didn’t waste all the money on corruption.
Russia is far larger and far less populated, it's an economic backwater and a cultural dead end. Yet despite that they have rail connecting their country together.
What is this corruption you are talking about? What specifically are you talking about? Things you don’t like aren’t necessarily the result of corruption.
"The US could too if they didn’t waste all the money on corruption."
China is also corrupt, but it is a dictatorship with massive central planning. Central planning leads to wastage and human costs in many areas but it is good at producing new infrastructure.
China also has nationalized rail systems. The major reason for the failure in the US is that the rail lines are not publicly owned. The reason the rail systems never got upgraded and Amtrak couldn't deploy high speed rail everywhere (despite it being a national priority in the 70s, 80s, and 90s) is that outside of the northeast corridor, Amtrak doesn't own the lines and couldn't get the owners to allow Amtrak to upgrade them for passenger high speed rail.