I have found that the plane time travel door-to-door is almost slower than land base transport, especially train. If I travel from Cologne to Paris, car about 6.5 hrs, train is 3.5 hrs, plane is about 4.5 hrs.
This is really a big issue. I notice more and more metro areas are pushing their airports way back to the hinterlands. Especially for inter-European travel it seems kinda pointless to use airports when it takes already an hour just to get from an inner city area to the airport.
This definitely depends a lot on the airport and distance you are traveling. San Francisco to New York, Los Angeles to Chicago... America is too big for land to be faster. Stuff is a closer in Western Europe.
You are right. The example I gave is probably a bit skewed to faster travel times. If I had chosen say Barcelona to Moscow, times would have been a lot different.
The other difference is that the trains in western Europe are much faster than their US counterparts as well.