Mostly dirt, but that dirt is also something that has to be travelled over to get between the people…and the scale of the US means there’s a lot more of it to span.

Inside a city electric trains make more sense, but unlike the EU there are very few places in the US between population centers that could economically support the infrastructure needed for high speed rail.

For example, Texas is roughly the size of France, but with only a third of the population, and hundreds of miles between population centers, none of which could expect to see the amount of travel needed to justify that much rail line.

Basically, take Europe and their economically viable rail line, get rid of 3/4 of the population and 3/4 of the cities so each stop is 3 to 4 times further away from each other and ask the people running the trains if they would still be profitable considering they’re still having to cover the same distances with a 1/4 of the income.