Somewhat. Russia doesn't produce a lot of the things the US produces. For wheat and certain other things sure, but for soybeans, for fresh green vegetables, for nuts, for fruit? A lot of that stuff Russia doesn't have the right climate for whereas the US has a uniquely diverse climate that allows them to from California to the plains and mid-west to the south to the northeast grow a variety of cultivars spanning everything from cheap corn and wheat to most every type of green vegetables, roots, nuts, fruits, etc. California alone has enough fertile soil and farmland to feed hundreds and hundreds of millions of people, maybe a billion if supplemented with grain staples from elsewhere.

As I said China won't starve thanks to their own work in this area and their friends in Russia but well the Soviet people didn't starve but they also didn't have supermarkets with fresh tropical fruit or often an abundance of typical fruits and certain types of vegetables were not in the fullest supply due to the constraints of what they could grow. Agriculture has advanced somewhat but there are still limits and being cut off from the US and its incredible amount of produce will certainly drive up prices for Chinese people. This is why I think the CPC had that push to reduce food waste. If this comes to pass the Chinese people will need to be a bit more frugal with food.

For China to truly replace the US they need to free from the grips of US hegemony and maintain good trade relations with parts of the global south in Asia and Latin America which is still a work in progress. As I said as long as US controls global finance they can cut off trade or make it very expensive and for perishable goods like food that's a real problem because you can't afford another stop in your supply chain in another intermediate country and routing through shell companies for all of this stuff and even for stuff you can it introduces another point of spoilage and rot.