This system is more fragile than you think. It would not be out of the realm of possibility for the food supply to simply "run out" one day, as there is an uncomfortable amount of price manipulation going on in commodities futures markets (for example, America ran out of soybeans last September, and no-one saw it coming). Combine that with a simultaneous currency crisis, which would hinder our ability to make up the difference on international exchanges, and you've suddenly got a lot of starving people. Don't be surprised when you start hearing of bread made mostly from sawdust. It happened in the Soviet Union.
There is also the situation where the government comes to crack down on "domestic terrorists", which will eventually include anyone who speaks ill of the ruling party. If you are burned out of your house, you "grab your gold and run" (an old Arab saying).
Gold is also small enough to hide on your person. A person can hide between 3 and 5 oz in a small bag tied behind the scrotum, which will be very difficult for anyone to find, even if you are strip searched (this is how the Polo family brought saffron to Asia, despite being robbed several times along the way). If you have an overly obese person in the family, you can hide an almost unlimited amount in the folds of their fat (considering a prisoner sneaked a gun into prison this way, it seems quite viable). Gross, I know, but these are last resort survival strategies.
I think we both agree on the fragility of the system, but disagree on how many people could perish from such a scenario. In the Soviet Union, many died, but there were many more who made it out alive.
Let's say the currency completely collapses, not a huge drop in value, but an overnight hyperinflationary scenario (which is how they always happen, but I digress). All American FRN's are useless. People will drop the dollar exchange and move to a local system based on something else (international currency, gold/silver, etc), or it could just be plainly on the barter system. The minute the dollar collapses, everyone doesn't just die. Currencies collapse once every 5-10 years it seems, and many people from the country make it out alright. A question for you, how many people do you think in the worst case scenario will die? I am betting no more than 150 million in the most catastrophic of scenarios.
Farmers will still farm and eat their own food, so they should survive. A smart farmer will grow even more food and trade this food away for items worth something in the new economy. People will start gardens outside their houses and eat from those. Canned foods will be huge.
The government will be bankrupt. It will slowly but surely completely collapse. When soldiers realize they are getting paid in hyperinflated currency, they'll just leave and rejoin their families. When police officers, firemen, etc realize the government can't pay them, they'll just walk away from their jobs.
You're absolutely right, and you're just hitting the tip of the iceberg. There are tons of ways people can survive, but most are not exactly preferable. But, you have to do what you have to do.
KIL: Agreed. I will laugh at anyone carrying around a brick of gold trying to buy food.