... any country would actually honor unenforceable "rules of the road?"
Well, the same could be said about most rules of the road. Nevertheless, most people trust each other to obey the rules of the road - I just crossed a green traffic light this morning and that friendly driver actually stopped for me.
Most rules, including international ones, are working if there is trust. Trust can only grow if the relevant actors show good behavior. Not all of them, but maybe a majority of them (see: traffic rules). On the world stage, the US used to set an example (not always, but often), but with the cold war mostly forgotten, they now seem to take the lead in destroying trust in international rules. Too bad, because who else would be trusted to lead? The EU is busy with its internal affairs, China is not really trusted -- how should you trust an intransparent party dictatorship that might change direction any day? Russia is busy making wars to keep its people distracted. It's a sad world where the sentiment that 'nobody would care about the rules' becomes the expectation. There used to be much more hope and enthusiasm about the UN, WTO, ... leading us into a better future. Now it just seems to become a race to the bottom.