Okay, let's look at that bullet train. At best that's 200 mph. A trip from SF to NY is then going to be 12.85 hrs. Assuming we go in a perfectly straight line (trains can't do this) and no stops. We'll say 13 for ease. A nonstop flight (not hard to find) is about 5.5 hrs.
In both situations we're only considering the travel time of the vehicle and not including anything like layovers/stops or boarding and unboarding. These are not one or two hour differences in travel time and thus security would make the difference, there are over 7hrs difference! You could fly all the way back to SFO before that bullet train rider gets to NYC (you're already through security). (We're also assuming that as trains get more popular that similar security theater isn't also introduced)
Now I do think people would still take the train fwiw because even with a 7hr travel time takes up all your day and flying sucks. Plenty of people will make this trade as long as trains don't sardine pack like airlines do. But let's also not fool ourselves into thinking the times are roughly the same and that that train also isn't going to take closer to 16hrs to go across country. Which even means doubling the speed (400mph) still makes it slower than a plane with security check-ins.