For me it works out like:
30 minute taxi to airport
2 hours ahead because its an international flight; checkin isn't even open if I arrive more than 2 hours earlier, I could get away with 1 hour or 1 1/2 hour, but I would get nervous.
1 hour delay on tarmac (b/c...Beijing)
11 hour flight
30 minutes immigration/baggage because Seattle is cool like that (unless our flight gets in early, then we have to wait for customs to open, curse that afternoon Beijing-Seattle flight!). On the other end, you have Heathrow, where the wait to get through customs is 4 freaking hours. I'm never flying to London directly from Asia again.
30 minute taxi to Bellevue if Seattle is my final destination (it often is), otherwise, hang out in the airport for a few hours waiting for whatever weird connection I have. Security in SEATAC is like 10 minutes, so no big deal there.
Bullet trains are great, until you realize that the bullet train station is farther away than the airport...on both sides of the trip! Given the distance, it's still much faster to fly between Beijing/Shanghai than to take the bullet train. Japan is completely different, of course.
I'd really like to hear if an Australian travelling to New York (or anywhere international but Bali/NZ) would prefer a faster plane.