I have a bit more time now to give a little bit better of an explanation on how food exports will be effected by this shutdown. One thing to keep in mind is though something seems a few years out, it doesn't mean that this is not a going to matter then.
For example, right now in the USA we are in peak harvest season. Let's look at just a few of the key commodities that have MAJOR downstream implications.
Soybeans $34 Billion per year
Corn $18 Billion per year
Wheat $9 Billion per year
Cotton 6 Billion per year
Oil $266 Billion
Now as we look at these raw materials we need to think about how that will muck things up down chain. Right now, barns and silos of manufacturers and other producers are low as reserves have been depleted since last harvest. With all of the ports shut down, this means the crops in the fields are going to be staying put. Also, a lot of these crops have already been paid for. To give an example, the warehouse I work in is almost back to a sense of "normal" from the big 2020 fiasco. It has taken 4 years for us to recover from the supply chain disruptions. This port shutdown will cause a panic buy outside of the USA by other countries to get their hands on whatever they can while the largest source of these goods is not moving.
Let's look at some of the industries that these four crops will have implications on.
Global meat production. Corn and soy make up a large portion of animal feed. With reduced supply in an industry that can't take too many hits without having massive losses, this could be big for other nations that depend on these sources for feed. Not having their barns fill up means they will have to either cut back which means the pigs, beef, and chickens are not going to be putting on enough weight at finishing time and will slash profits of those producers.
Let's look down from the animal protein industry for a minute. This could also cause supply issues with leather industry in those countries. If you have a disruption of animal slaughter, you have a disruption in leather goods, etc.
Look at cotton. Texas produces almost 1/3 of the global supply of cotton. That mostly gets exported to 3rd world countries that then make goods from it and ship it back. If the cotton cannot leave port, the raw materials for manufacturing aren't going to be there to manufacture with.
Now let's look at oil, the USA produces 20% of global oil. Port Houston is now shut down creating an even further squeeze on oil and gas supplies that have already been hurt.
One thing to keep in mind, is each of these materials is the raw material that then in turn makes the rest of the industry move. All it takes is one critical piece to fail before an already fragile supply chain can have problems. One way I put it to people is this. You can have a $500,000 Lamborghini that can go over 200mph, but if you don't have lug nuts for one wheel, it ain't going nowhere. It is the insignificant things which can be the most vital.
This is just a slight bump to cause a couple of dominoes to tumble that could easily set off a chain of events (I believe all are planned) to create a need for the solution that is already there.