I think they will eat their storage of foods. Ammunition will be used for hunting or passed on to their kids.
I haven't been concerned with a Mad Max style society of everyone fighting for food and such. My prepping has been against the left's slow boil approach to controlling our access to energy and transportation. They push their policies, ostensibly to save mother erf, and make it harder and harder to produce energy, and more expensive for the consumer to buy it, with less suppliers for refining oil into gasoline, and regulations that make it more expensive to drill for natural gas, and regulations that force power companies to shutter coal plants and replace them with natural gas fueled plants that already have rising natural gas prices they have to pay, or make power less dependable by making the grid depend on intermittent sources.
Right now most Americans' energy costs are bearable, but more expensive and less dependable than it used to be. When the left gets back in control they'll turn the slow boil up a little more, then a little more. Until they bankrupt us by us trying to simply cool and heat our homes and drive.
Hence the reason for our home solar project, and the energy improvements to the house, and converting one of our cars into an EV so that at least most of our local driving is powered by homemade power. This year we spent $1,100 in energy for our home (just power bills because it's now all electric) plus local driving (what little we drive the gas pickup). All while driving our EV 16K miles in home charged miles, and keeping our 2,300 sq ft home comfortable.
Will it be worth it? So far it is. The loan payment I make to pay for all of those improvements, plus the small power bill, is less than would have paid in high power bill + high natural gas bill + lots of gasoline at the pump. The energy portion of my budget is fairly predictable (it's not like the loan payment is volatile and based on the price of oil or the Henry Hub price of nat gas). And by not spending as much on energy, it equates to not having to pull as much from our Roth IRA's (or if I'm working, it means more I can put into our Roth IRA's and sometimes Roth 401K).
Would that work for everybody? Not unless you live in the deep south where we get tons of sun. (By deep south I include the southwest.) And an EV won't do unless you need two cars (married) so that one of your car is a gas car for the times an EV won't do (i.e. pickup chores, or long trips in areas with few charging options, or trips up north during the winter). Also, an EV is unwise unless you drive tons of home charged miles to get the gas savings.
But everybody ought to at least do the research to see however they can make themselves less dependent on energy or anything else the govt over-regulates.