All you have to do to evaluate the threat is look at what the government has done. There are underground complexes stocked to support lots of people, presumably government leaders, for years. Sadly most of the elected are hardly the kind you want to base a new society on. A few years ago someone published a book who used to work in the Congressional Travel Office. She just recounted some of the interactions she had with Congressional members. Some of them are extremely stupid. One situation I remember from the book was that a congressman was going to Orlando Florida and wanted a room with an ocean view. When the travel office person said Orlando was inland and that was not possible, the congresswoman was indignant and said if you look at a map, Florida is very narrow and you should have an ocean view with a West or East facing room. These are the kind of people that govern us.