Once the US has one working world-class HSR line (probably Brightline West, or possibly CAHSR), the appetite for more lines will increase. HSR will have become something that is common for Americans to ride when not on holiday to Japan or Italian hilltop towns, and reflexively dismissing it as “it wouldn’t work here because we have too much (space/liberty/big cars)” won’t work anymore. New plans will be proposed (a midwest network connecting Chicago to Cleveland and St. Louis?) and old ones (such as the Texas one) dusted off. And the Canadians will notice and jump on the bandwagon (given that a big chunk of their population would be reached by a line from Detroit/Windsor to Quebec City makes it a no-brainer).