Assuming that your travel takes you within a 300 mile radius (I travel by air about 50,000 miles per year, mostly within the US and Canada, and very few of those trips are within 300 miles), *and* everywhere you want to go is served by the rail system to within 10 minutes of a subway or bus, sure. Unfortunately, even with this plan, that won't happen.
Your numbers are fairly compelling, for those 300 mile trips. Don't get me wrong, I'm all for a well run, efficient, high-speed train system.
I live in the Dallas area. If I was going to, say, Houston - that's right inside your 300 mile radius. As I've done this trip a number of times, it looks something like this:
Drive to airport, park, shuttle to terminal, check-in, security : 60 minutes
Wait for boarding: 30 minutes
Taxi: 15 minutes
Flight: 45 minutes
Taxi: 15 minutes
Deplane, get to rental car: 30 minutes
2:45
Estimate for rail:
Drive to train station, park, check-in, security : 45 minutes
Wait for boarding: 30 minutes
Trip at 300mph: 60 minutes
Unload, get to rental car: 15 minutes
(I'm assuming that with a well run high speed train into Houston, rental car agencies would set up shop at/near the station just like they do at airports)
2:30
In other words, my expectation is that they'd be about the same. The rail experience would have to offer something that air-travel doesn't; cost, comfort, service, etc.
In this scenario, were the prices similar, I'd probably take the train. Better scenery, similar time, less stress, most likely more comfortable. I'd even take it if it were an hour longer given those factors (though it would have to be a cheaper option at that point).
The problem is, no one has yet be able to do a passenger rail system in the US that competes on cost with the airlines. Amtrak is very expensive, takes way too long, and is really (in my opinion) only an option on long trips for people who refuse to or cannot fly. With Amtrak as a comparison, the tickets would be twice as much and on-time half as much (which is saying something).