Let's not confuse domains: while economics isn't (necessarily) zero sum, geopolitics (in terms of influence or territory) is. US policy has nothing to do with these two facts.
Yes, when you look purely at geopolitics in terms of influence or territory, then that's zero sum.
But even when leaving economics out of the equation, which I find questionable, there are plenty of other aspects of politics that are not zero sum.
For instance: climate politics, pandemic control, arms race prevention.
I don't disagree, but they all unfortunately take a backseat to geopolitics. When it comes to the behavior of nations, the playground politics of bully and victim has more explanatory power than all the high talk of the UN.
But is that really true? I wasn't talking specifically about the UN, but if you take a look at nations across the globe, also historically, is the behaviour of nations primarily ruled by zero-sum bully and victim politics, or by nash equilibria, i.e. compromises where both parties benefit? I would say that nations that are at war or threatening each other with war are in the minority, globally.
Hmmm, you raise an interesting question. I'm no game theorist, but are bully/victim dynamics and Nash equilibria necessarily mutually exclusive? What I'm getting at is: the threat of force determines every other player's optimal strategy, with a fight always being the last resort for everyone involved.
Under such conditions, Adam giving the bully his lunch money, Bob his homework, and Charlie his lunch may be the Nash equilbrium—that is, until Dave (who knows kung fu) moves to the neighborhood.