Factor in time wasted at the airport when you show up early because the TSA is unreliable. I always give myself at least an hour extra and sometimes that's cutting it razor close.
And frankly not being subjected to the TSA is generally worth at least a few hours of my time. I'll sooner drive six hours than fly one because of those worthless assholes.
Then you can just build a conventional 300kph high speed train and track. They are 'off the shelf' commodities these days.
It will still be competitive with flying.