There is an old saying in the military that a plan is good until the first shot is fired. If you have ever been involved with creating and executing any kind of large scale plan, military or not, you know this is true. This leads us to one of the reasons why the idea of the Federal government sending in troops to take over every little small town and rural area has a few problems.
In a major survival situation, it is reasonably probable that the top Federal officials will get to their bunkers and be safe. After that, the odds drop with each level you go down. The state government officials may or may not safely get to their “emergency command centers” which will be less protected than the Federal government’s bunkers and the County officials will have a greater chance of not making it to their “command centers” or not surviving in them after the event.
But even IF all of them do, you then have the problems of communication with the “muscle” necessary to carry out their orders if their “muscle” even survives to be used, or can be used as they wish. Again, the Federal government has the higher odds of having the communication and the “troops” intact for use. But they also have the entire country starting with the major urban areas to deal with. The State governments will vary with the state, area they have to cover (Rhode Island versus Wyoming for example) less stable communications, and loss of a good chunk of their “muscle” (National Guard) to the Feds. Finally, on the County level, there is the advantage of less area to control and the possibility of communication by messenger, but low levels of “muscle”. This varies due to the makeup of the county. In some counties with urban areas, the local police forces will be left to deal with the situation with some possibility of help from the Fed. Others have only a sheriff and a few deputies instead of a fair sized force of “County Mounties”. The local police forces, if they and their communications survive, will either have their hands full in the major urban areas or on the small town and rural level, may not follow orders to suppress the people.
If you want to see an example of how this might play out in an apocalyptic type event, check out the old post-nuclear war movie “Threads” and note what happens with the local “emergency command center”. For a less “end of the world” type situation, check out what happened to the command and control in situations like Hurricane Sandy and especially Katrina. You will see that the situation could come down to the “leadership” surviving but the “troops” out of action due to causalities, lack of mobility or communications (EMP), or refusal to leave their families or act against their own people. You would end up with what we used to call in the old pre-PC days as having “too many Chiefs and not enough Indians”.