Nothing precludes nuclear weapons entirely, but having to nuke "civilized people" (i.e. whites) or "fellow Americans" is a tougher pitch than nuking China or Iran. And even if the US nukes the US, that isn't as likely to escalate into a full world-ending nuclear exchange. I could even see the UK or France take a nuke to the face from the US without sending ones back because they don't want to have their country glassed. Let alone if it's Canada, Germany, or another ally of the UK or France.

Also, the US state has committed to exacerbating climate change to the point of human extinction. I see very few possible futures where the US state is not dismantled in the next 20 years where humanity survives the next 200. Exchanging a reduction of the chance of human extinction through climate change for a smaller increase of the chance of human extinction through nuclear warfare would be a good deal.