How many nuclear weapons does the US need to be safe? If the US is afraid of 10 nuclear weapons in Iranian hands, is China afraid of 5000 in US hands?
How many are on land and how many are in submarines?
What and where is something that matters in determining how many.
A rogue nation with a couple of nukes is much more likely to use them. Especially when facing a leading superpower that “isn’t” because the commander in chief has taken nuclear response off the table.
Israel holds the deterant against Iran, not the US.
China has been building nukes since the 1960s. They need the missile technology which Bill Clinton helped them with.
It's not the technology that we need to fear. It's more the form of government of the nuclear-armed opponent. Democratic-Republics are pretty stable & predictable. Dictatorships are unpredictable in the extreme. So to answer your question: I'd be far more worried about North Korea, Pakistan or (hypothetically) Iran than I would Great Britain, France or India.