Nature abhors a vacuum. Government never collapses. Some governments collapse, but they are instantly replaced by some other kind or form of government. Even an event as apocalyptic as the fall of the Roman Empire didn't mean the collapse of government. Barbarian 'governments' were already everywhere, and most were huddled under the iron umbrella of the Catholic Church as well. Life went on. The new age was a bit darker than before, but se la vie. Even the Black Death which killed off as much as half the population of the entire solar system didn't bring about the collapse of government. Governments are, for better or worse, resilient, flexible and adaptable. Better yet, they are easily and quickly replaceable.
If the U.S. Federal government collapsed, there would be temporary financial panics and complications - especially for retirees, the disabled and other dependents, and some high-stakes maneuvering over the military assets that were once controlled by the Pentagon, but there are still 50 state governments in place, 3,033 county governments, and thousands more incorporated cities and towns. All with entrenched, functioning bureaucracies, taxation and funding protocols, and all with paramilitary police forces. Even if the national government sinks into the quicksand of history, law and order aren't going away anytime soon. No doubt, regional 'national' or 'federal' arrangements would be quickly made between groups of contiguous states to strengthen what's left of our civilization. The collapse of the U.S.S.R. and its Warsaw Pact allies showed the world that cataclysmic political upheavals, including the mass secession of constituent political entities, can be done with very little inconvenience to the great unwashed.
America is unique among the great powers in that it is still, despite the best efforts of liberals, rather decentralized. To overthrow the government would be practically impossible. Where would you begin? Washington? The 50 state capitals? The 3000+ counties? Would Tennessee care if you overthrew New Hampshire? or Colorado? Would California, New York or Florida submit to a coup in Washington? Hardly. And don't even think about Texas. Just don't mess with Texas. The collapse of the national government is the last thing I really worry about.
What is much more likely is that local disturbances - either man-made or natural - bring temporary breakdowns in the orderly delivery of essential services like electric power, organized food and water distribution, medical care, fuel, fire and police protection, etc. It is for those situations that I prepare. Beyond that, it gets a little silly to either prep, or even worry.