Not completely. You're more likely to get external help to prop up your regime iff you have nukes and the external forces think it's better for your regime to stay in power than have a revolutionary force control the nukes. (Of course, if the external forces would rather the revolutionary force, then it's not so helpful)
For every country that has nukes, some countries will want them in power and some will want them deposed. You can assume both forces will be operating at all times (which to be fair is also true of pre-nuclear countries)
Hostile foreign countries are however much more likely to pour resources into fomenting a revolution if you have nukes as this would avoid conventional warfare which has the potential to escalate to the point of nuclear deployment.
In the context of Iran vs. North Korea which this discussion is in reference to, Iran is very likely to fall from internal forces which overwhelmingly disapprove of the government, compared to North Korea which seemingly has overwhelming support from its people, and has been cut off from the rest of the world since before the Internet was available.
It's unlikely another country will ever be capable of instituting the same degree of isolationism that North Korea has, owing to the prevalance of internet-capable devices everywhere else in the world. And honestly I don't think the North Korean government would have survived as long as it had without this policy.
