But if that ever actually happened, those countries could blockade the United States and cut off the food supply. It would be a shitshow. Imagine the 1970s oil crisis, but instead of being unable to drive anywhere, mass famines occurred.
In Canada, we don't use subsidies for the dairy market. We use "supply management" where we make it difficult to import butter or milk and ban farmers from producing too much of it. This keeps the prices artificially high which allows for farmers to continue domestic production in a HCOL country. However, 4 sticks of butter costs $6.