Saying progress in the UN is held up by Iran and such sounds nonsense to me. The US is also pretty conservative and has way more influence and power inside their buildings.
I only have a friend's word for this (who works with drug policy), so if you know more please share. Obviously the US drug policy is quite varied, with full legalisation of marijauna in some states. The federal response to the opioid epidemic seems to be harm-reduction based rather than purely punitive. That said, this is internal politics, so what the US says and does on the world stage is not necessarily going to be consistent with this.
