There's 2 types of public transport: intra-city and inter-city. Intra-city doesn't serve the same use case as flying, and can't generally be repurposed to inter

There's 2 types of public transport: intra-city and inter-city. Intra-city doesn't serve the same use case as flying, and can't generally be repurposed to inter-city transport, so it should be discounted. If the US had inter-city rail that people actually used, then it would almost certainly be near capacity in a normal holiday season. Unless you assume there are a lot of extra train cars that aren't normally being used but could be taken out of storage, there's no way that it could absorb such a large influx of stranded passengers on short notice. Inter-city rail generally operates like airplanes in that only one ticket can be sold for each seat - there's no standing room on a multi-hour train ride.