Yeah I know but thanks for the links. No question it will get bad, but it will be worse almost everywhere else in the world. The US has much more land compared to the population than it’s rivals.

That's a bold statement, and not really sure what you base that on. For example, it's almost certain that things won't get as bad in Russia or Canada. The reality is that global climate is an incredibly complex system and nobody really knows how bad things will get, and where it will be the worst. For example, it's quite possible that it's actually cooler climates that will end up being more affected because that's where the most drastic temperature changes will happen as opposed to places that are already close to global maximum.

In the extreme you only need about 90000 km² arable land (~ size of Indiana) to grow enough potatoes to feed the entirety of the US (napkin math).

Actually turning all that land into farm land would be a monumental project. The US isn't even capable of maintaining its bridges right now that are at risk of imminent collapse, you really think that the US would be able to mobilize to turn a land area the size of France into effective farmland in time? https://www.popularmechanics.com/science/a62073448/climate-change-bridges/

My point is this: Starvation won’t be an existential threat to the US. Two oceans provide a lot of security, and options for geopolitical strategies. The only thing that can destroy the US is the US itself. Or nuclear war.

The problem here isn't purely technical, it's a question of policy and logistics. The US is a dysfunctional state that's not capable of marshalling large scale projects. Dealing with climate change is going to require a level of organization that's simply not present in the country.

While conflicts and collapse of global trade could easily make starvation an existential threat or “threat multiplier” for Europe, India and China. And many other countries on their large and porous borders.

That's one of the reasons both China and India keep Russia as a close partner. Europe is likely very much fucked however. Also worth noting that China is now leading the world in indoor farming, which is one of the best ways to mitigate unpredictable weather.