You'd only want to build regional HSR systems that would connect cities that get a lot of traffic and flights between them and are under 300 miles / 500 km apart. So, the northeast corridor, connect California major cities, connect Portland to Seattle, connect Dallas/Austin/Houston/San Antonio.
In Canada, half the population lives near a nearly straight line from Quebec City to Windsor; you could put a high speed rail line down the middle of that.
In Canada, half the population lives near a nearly straight line from Quebec City to Windsor; you could put a high speed rail line down the middle of that.