This is probably true, but I don't think that at the national level the votes are there yet for a dedicated funding source for passenger rail the same way that the highways have such a source in the fuel tax. But it's true that once there's a pot of Federal money that can go to the states and be used only for passenger rail projects, there may be more interest in such projects.
But you still can't discount the power of ideological opposition to government funding of such things. Consider the case of Merritt H. Taylor Jr., the owner of the
Philadelphia Suburban Transportation Company, one of the last fully privately run transit companies in the US. He was very conservative and believed the government had no business subsidizing companies like his. He resisted all forms of regional cooperation, especially with governmental entities like SEPTA, and kept his company private for as long as he could. However, in the end, he did sell out to SEPTA. The ideology is still there, which is why there are a lot of people rooting for Brightline, because they're not taking government money. The problem is, I'm not sure the Brightline model can be repeated in other places. Even their Las Vegas line is not really going to work without partnering with the publicly owned railroads serving central Los Angeles.