If society breaks down to the point that many envision and the government reacts the way they say then they are dead. The government will go door to door collecting resources and disarming everyone. If you resist, they will simple blow up where ever you at. They will fly around with FLIR looking for hold outs. They will look at satelite maps for signs of you. They will look through tax records when you just disappear.
All is not lost as there are things that will have a happish ending if you were a little prepared. I broke them up into three groups.
Everyday senarios that you should be prepared for as they are most likely:
1) You loose your job or lose income.
2) You or member of your family becomes disabled.
3) Local crime rate goes up.
4) Inflation takes off or Deflation takes hold.
5) Taxes get raised insanely.
6) You have legal troubles.
The senarios that are most likely but not everyday type stuff and you should be prepared for:
1) a 3-5 day localized severe breakdown of order due to social upheaval or natural disaster. This is why you should have firearms and the skills to use them.
2) A localized breakdown of supply in the neighborhood of 7-28 days possibly associated with the previous or due to a cut of petro supplies or economic crisis. This is why we prep.
3) An attack on a major US city that kills tens to hundreds of thousands causing 1 and/or 2. This will happen at somepoint because we let our enemies make highly enriched nuclear fuel and no one has ever failed to make a bomb after obtaining it.
4) A honest all hands on deck war like WWII, if overseas then preping will be a goodsend, but if here then firearms and skills will be needed along with the prep.
5) Civil war or oppressive Hugo Chavez type government, which could cause intemittant 1 and 2 with lots of shortages.
6) A biological threat (affecting humans or food supply) spreads across the US causing 1 and/or 2.
Unlikely events (but have happened while humanity has been around):
1) A dorminant volcano near/in a major population center becomes active and disrupts/displaces large numbers or people.
2) A super volcano erupts causing mass crop failures or maybe killing most everyone in North America.
3) A smallish comet/asteroid creates and air burst.
4) A very large earthquake in the ocean causes a tsunami across the entire east or west coast (East Coast has known threat).
5) Full scale nuclear war. The prep and planning required to guarantee survival of this is beyond most people's finances and realistically may not actually be possible.
6) Large asteroid. Requires luck and see #5.