Russia has 5192 warheads. America has 4102. France has 300. So how many warheads can destroy the whole world? Here are the statistics of different countries possessing warheads.
What this means? We only actually have 0.83% of what’s required to completely wipe out civilisation. We couldn’t do it if we wanted to.
But we all live in cities now. 50% of us live in densely populated cities now. Maybe we could wipe out all city-dwelling humanity. YES!