It takes a lot more than one nuke that works. They would need hundreds of strikes, probably thousands to ensure they aren’t immediately annihilated in response. There is a game theory to nuclear warfare, and dropping one city buster on a nuclear armed adversary is the sovereign equivalent of suicide-by-cop.
If this is the case, do France and the UK even have a nuclear deterrent? They have just over 500 weapons total between them - is there any chance that they are able to “ensure that they aren’t immediately anihalated” by a Russian response?
For reference, that number of nuclear weapons is where China decided to draw the line as a nuclear deterrence against the US until recently.
A hundred modern nuclear weapons is plenty to fucking ruin a country, but no, it doesn't not take "just one". Most western countries would survive say, a smuggled terrorist nuke (or 4) just fine. Angry and mourning, but fine.
France alone has enough deterrent in their nuclear weapons. The UK has theirs in submarines, to ensure even if you magically erased the entire British Islands, you still take tens of nukes up the ass.
Nuclear deterrence is not complicated, and it's pretty well understood in public. I don't know why so many people here are so wildly off base.
Meanwhile, all this was always intended to be roughly "backup" to the US's absurd stockpile, including tons of literal gravity drop nukes so we can cosplay Dr Strangelove as the world ends. And the ending of the IRBM treaty means the US has recently told our defense industry that it gets to play with the cool rockets again.
