I believe that a crisis would have to be created for rationing to have any acceptance in the US. What form that crisis takes shape in would be anyone's guess.

Without a exterior demand on supply, like wartime, I think that the approach (as OP mentioned) will be to let the markets set the price and to subsidize lower prices for as long as possible.

It is my opinion that we are already seeing this rise in prices in our sale prices. A year ago you could buy a pound of butter on sale for $2, now sale prices are $3. Campbell's cream of mushroom and chicken noodle soups could be had for .50 each if you waited but the best price that I've seen this year is .59. Most telling for me this year was the sale of canned vegetables. In the past there would be a week sale at .49 a can, this year they only had a two day sale at that price.

Also, pay attention to what is on sale. Not as many staples and canned goods but plenty of junk foods.

People who buy whatever they want without regard to whether it's on sale won't notice anything is wrong for a while. More frugal shoppers are already noticing. I would think that rationing would be instituted only as the supply chain was at the point of breaking down.

My guess is that we are a few years off from rationing unless the harvest this year is worse than even the GSM crowd thinks.