> why would anyone trust usa's word if any agreement/word/promise can be torn unilaterally?

I suspect we're going to see the answer to that question play out over the next several years.

I agree with you, I'm trying to add color to the situation by pointing out that America has benefited from this invention stemming from the conditions of pax americana where the alternative is international law via the UN and ICC and other institutions that are perhaps more independent than the US would like.