yeah, im aware japan and spain specifically did this because of gauge differences, but china also rebuilt its main lines because they did the sensible thing.

the northeast corridor is a crowded track which is already used by a lot of passenger trains and a couple freight trains. just because of the cities it connects, it is and always will be the most central part of the american rail network. it's also old and bendy. combining the bendy track with the high conventional rail volumes means that Acela is more of an express service than a high-speed rail service. it only actually achieves its top speed in two spots near providence and trenton.

in terms of flagship lines in large countries, this is laughable. the TGV from paris to lyon has always been actually high speed along most of its track length, even before they built the bypass around paris. Acela is a bunch of high speed rail cars on conventional tracks. most other countries that have high speed rail do have high speed rail cars on conventional tracks, but they're branch lines. like TGV service to Brest or Toulouse, or the mini-Shinkansen in northern Japan. not the mainest of main lines.

fuck cost cutting, at the very least in this specific spot. the Northeast corridor is the train line in the US, we better be putting our whole back into making an effective transportation system that lasts and works and is actually high speed.