That's your opinion. Whether it's true or not is debatable. However, that's not what this thread is about.
Now, as to whether "if it were such a great idea and it could be profitable private companies would build it", the same concept applies to nuclear power plants. They actually are a pretty good idea. And they are very profitable
once they are built. And they're a fairly good cost effective alternative to fossil fuels from the Middle East. So, why hasn't a new one started construction since the 70s?
Answer that, and you'll have the answer as to why no private company wants to build HSR in the US (or anywhere else in the world, for that matter). Sort of self-evident, if you think about it, really...