I'd say the cut off time is more like four hours, with the delays incurred by airport security and the fact that airports are huge and therefore more likely to be located further out from city centres.
In France they closed flights up to 500km competing with TGV.
500km is less than 2h in TGV, you show up 5mim before departure, you have no annoying security check and stupid questions asked, and you arrive in city center. Planes cannot compete with this offer.
Even more since SNCF launched their low cost TGV (Ouigo).
Sure, but building a rail network that is able to compete with four hours of flight is orders of magnitude more expensive than building out decent HSR between major clusters of larger cities (e.g. California HSR).
