There's a surplus, just no way to transport it
In the US we typically raise crops in such volumes that we can largely export many of them. We also raise an abundance of livestock. With the current drought happening in the Great Plains, many corn and soybean crops failed. A majority of livestock is also raised in this region since grain is located there.
Most crops and livestock are grown on corporate farms. The way that they can exist is by transporting supplies toward their production. Then at harvest, this transportation system relocates the crops and livestock to the consumer.
Of course it doesn't flow directly. They're sold to middle men who in turn sell them to other corporations for inclusion in preserved products. Then these are purchased by other corporations who send them to distribution centers as places to warehouse them prior to shipping to retail outlets. That's when the consumer actually gets the products.
All of those steps are monitored such that each movement is minimized. The longer something is warehoused as a component of a final product, the more cost is incurred towards its production, and this cost is passed on in part to the consumer, but based upon competing with other corporations that also sell that item.
A system was developed for inventory control. If a program could minimize ordering supplies and only created products based upon projected consumer sales, and minimized surplus inventory as components and finished product, then each corporation along the chain would have higher profits. The system was created in Japan and it's known as Just-In-Time manufacturing processes. (JIT).
While we do create a surplus of food, we don't let it sit in warehouses mostly. Yes, there are peak seasons with food. It's not like other products. It's grow, and harvested, but many of these corporations purchase from foreign countries. Their growing seasons may be quite different than our own. Still grain sits in silos, because it's possible, but of course we can't let apples sit long, or they'll spoil.
Now food is not the only product, but there are many other kinds of supplies, and these perhaps have longer shelf lives, and they are often created upon demand. This is why it's very possible for shortages to occur, and so transportation must be a finely tuned delivery system to both measure consumer demand and anticipate it as well.
If there's a dollar collapse, vendors will not know the value of the currency. Mistakes will be made, and profit lost, and this creates hesitation. That creates a slower system and shortages. Since many products come from foreign countries, they won't know the value of the dollar. It will be determined by market forces and trust and based upon the perceived stability (or lack thereof) of the USA and expenditures and potential growth.
Of course, we don't spend money that we take in, we borrow it (US debt instruments, corporate bonds, municipal bonds, stocks, mutual funds, etc) because we have a negative cash flow problem that will never create a net positive result. This lowers the value of the dollar too.
We artificially create more money by food stamps and unemployment expenditures (and lots of others), and so we have inflation. This lowers the value of the dollar too.
Other countries don't want our dollar, and why should they? A desire to switch to a stable currency will eventually cause a collapse when inflation gets so high and demand falls so low, that it's no longer in other countries benefit to use it or accept it.
When that happens, then they'll have to weigh which currency would be better versus the military might of nations versus global security.
Up next: Many countries have worse deficit spending than the US. It doesn't have to be an initial collapse of the dollar. It could happen elsewhere and cascade.