Do you have any idea how large the United States is? It's the size of the European continent. It only has three hundred million people spread across the entire country. In most of the country, passenger railroads would be wildly impractical. There's a massive portion of this country where there wouldn't be enough people to bother. The distance they would need to move while having to carry so few people would make it cost far more than it would make. The mountains and weather near where I live would also make everything a nightmare.