Fortunately those countries don’t have those capabilities and Russia and China are not about to give them those capabilities, and just because they are sublaunched and only kills half the US population is not a prescription against Argmageddon against the perpetrator and for something like that we would know who the perpetrator is.
You think, North Korea is dirt poor but somehow managed to build an ICBM capable of hitting the US mainland.
To think that China didn’t play a part in that is naive and to think if North Korea has the capability, then Iran probably has the same capability.
My point, is technology can’t be bottled up and kept to 2-3 countries, countries like Pakistan has nuclear weapons, at one time South Africa has nuclear weapons, there is no reason to think North Korea or Iran don’t have the same technology.