If you want to say something then say it. No, I don't think there's any particular physical reason for that; I think the poor state of north american passenger rail is almost entirely for political reasons and could be changed if the public had the will to improve it.
Beijing and Shanghai are two of the most important cities in the world. Minneapolis and Toronto are not. Of course it’s physically possible to build a high-speed train from Minneapolis to Toronto, but it makes little sense to do so unless you’re building all the O(n^2) point-to-point links between all the medium-importance cities in North America.
