If it happens it happens. The minute Russia sets off a nuke, no matter the size, Russia will be a sheet of glass from dozens of countries around the world. It childish to threaten nukes, mutually assured destruction means what it says. Lots of countries have nukes, and many countries hate Russia. The US doesn’t but nobody ever said the Russians are smart enough to figure that out.
The fact is, faced with an existential crisis any nuke equipped nation will start lobbing ‘em rather than being destroyed - the US has done it just to hasten an end to a war that would have ended in the US’ favor anyway.
“The minute Russia sets off a nuke, no matter the size, Russia will be a sheet of glass from dozens of countries around the world.”
The Dunning-Kruger effect is real.