Continuity of Government in extreme emergencies is necessary. The govt has planned for this and over the 3 year period of 2018-2021 have moved from low threat level 4 to immediate threat level 2. We remain at level 2 while things are being sorted out.
What is CogCon https://whitehouse.gov1.info/continuity-plan/
Elevation from 4 to 3 happened in January 28th of 2018 https://antinwoforlif3.blogspot.com/2018/01/cogcon-level-3-continuity-of-government.html
Elevation from 3 to 2 happened in January 8th of 2021 https://www.youtube.com/watch?v=SahUck6wVYk
Actual exercise conducted in 2014 https://medium.com/homeland-security/life-at-cogcon-1-c60083f923ef