Futurology

Okay, lets say making it a "subway" works, and ignore the issues with digging out a tunnel for repairs/etc.

The issue is now tunneling hundreds/thousands of miles over a varied terrain. That would be hilariously more expensive than building standard high speed rail, likely 100x or more, which at 300km/would do the 226km Vancouver to Seattle trip in 45min. In contrast, at the max 1000km/h of this theoretical bullet train, people are making the trip in 15 min instead 45min. Is that small difference worth the wild expense?

Is having 1 route be 15min instead 45 better than 10 or 100 new "vancouver to seattle" routes that take 45min?Assuming its even just 10x as expensive, you could put a HSR train down the entire West coast for the same cost of that single 150mil ultra high speed run.

Ain't exactly a good trade.