i.e., like how the US currently runs the global financial system and there is no real alternative yet.

I'm not an expert, but Ive heard the use of US dollar as the global reserve currency has already declined by 30% somewhat camouflaged by a healthy international economy. If that is true and continues, it is likely that USA as an internationally favored stock exchange will decline too. Because investor money will not flow to USA as they used to.

The US and Ukraine are not military allies

True but Most European countries are also NATO countries, and Russia is definitely a threat to Europe, that is widely acknowledged. So 100% USA is failing their allies, and then USA has the audacity to complain that Europe isn't helping in Iran, an illegal war that USA themselves started together with Israel.
NATO is not an American offensive pact, although traditionally we have helped USA in their global offenses, but that is because those were LEGAL actions, and it was agreed on beforehand, and there was an actual plan. All this the current administration has failed in completely, and then they come running afterwards and complain nobody is helping. 🤡 🙄 🤮

the US and Russia are not military enemies in a formal sense.

Bullshit, that was the entire reason for Cuba crisis that nearly caused a third world war, and for the entire cold war that lasted for decades.
There was only a pause after the Soviet collapsed, then Russia became like the old Soviet Union, threatening neighboring countries, and sabotaging USA, Europe and NATO in an absolutely cold war fashion. So no doubt Russia is the enemy of USA. Problem is that so is Trump, and he aligns with Russia as if he were a Russian asset. Except my guess is that Russia is controlling Trump by exploiting his greed, and Trump himself is unaware that he is an active asset for Russia.