Yep, it's not a Party-born issue, it's the funding source. Planes and Trucks are supported by better-hidden funding; highway construction (originally justified by military transport needs in "emergency" (the Interstate Highway system was developed initially to provide fast transportation of military goods). Airport subsidies are similarly justified, and then there's "rural access" subsidies for unprofitable airline routes.
AMTRAK's problem is that it is a directly-funded line item, and so is subject to too much scrutiny and an easy target for "budget cutting." Hmm, if we could fund train stations like airports are, and traffic control systems (air traffic controllers), the situation would be much different.