Light rail runs on train tracks and is almost all electric. Light rail makes up a lot of miles of railway.It's a diesel.
It needs diesel to run.
Cannot run without diesel.
There are no electrified train tracks anywhere.
All "electric" trains are powered by another source (power plant). Diesel Electric locomotives are designed to carry their own power plant.
Be it coal, nat. gas, hydro, nuke, sun, wind, etc.... the juice has to come from somewhere. Sun and wind (and if droughts persist, hydro) are intermittent so unless we build more nuke plants you're going to have to burn something to power trains.
Please don't try to compare the US to Europe when it comes to hauling freight by rail. In the US our railroads were built to haul freight and in Europe, railroads were built to haul people. And, unlike in the US, which is a huge country and has standardized rail gauge, in Europe, rail gauge and electric power supply varies county to country. Very little freight is hauled in Europe by train as a result.