This is always such an interesting topic. I remember doing a project on this in school. This would be such a nice upgrade for the public.
The tough thing is how much US rail & land is privately owned by commercial operators. Plus virtually all of that rail would need to be redone to accommodate HSR. Additionally, I think tickets would often need to be subsidized to be competitive to alternatives in many cases (some regional flights will already likely be the same price as what commercial HSR tickets would be).
The cost always makes it tough to justify versus other potential places for the government to spend its money.
Not that I wouldn't like to see it done. I think having HSR would be transformative for America in a great way.