I think generally true, but it can vary by geography. There are a number of Republicans from small to medium-sized towns that either have Amtrak stations, or would like to have them, who are supportive of passenger rail in some form, and some of that support bubbles up to Republican Senators in some states. That's one reason the Amtrak national network continues to hobble along. If its fate rested on purely party-line votes, it would've been killed years ago. For example, Kansas's senators joined with Democrats to keep the Southwest Chief route from getting axed. Texas and Oklahoma, both pretty red states, co-fund a "state-supported route", the Heartland Flyer, from Ft. Worth to Oklahoma City. For somewhat different reasons, Utah has also invested in commuter rail (FrontRunner).

Indeed. People on the right wing are saying that Biden’s new infrastructure bill is nearly all pork because only 5% is dedicated to roads. Really only roads and dams count.

I think in this case the demographic split actually is correlated to the merits. As in, if you’re in a dense city, you’re probably more pro-rail, because you’ll be the one actually using that rail. If you’re in a culdesac suburb or even further from the city, you’re likely to not be pro-rail because you won’t be using it.

You could call that tribal, or you could just call it “voting for your interests”. It feels slightly different from the tribal issues I see more frequently (policing, healthcare, schooling), but maybe I’m fooling myself.