In life, there are some old cliches that are often used in conversation. Two examples spring to mind:
“The grass is not always greener on the other side”
“Out of the frying pan, into the fire”.
Both of these are cautions against impetuous decisions to walk away from a situation that is perceived as bad, only find yourself in a far worse place. We have probably all come across people who, failing to take these sayings on board, and suffused with a mixture of anger, frustration and hubris, proceeded to show that you can indeed swap a poor situation for an even worse one.
Right now, in the world of geopolitics, the USA is faced with two sub-optimal scenarios, both involving countries who, feeling threatened by larger and more powerful countries, determined a long time ago that the way to improve their bargaining power and military position was to create the capability to assemble nuclear weapons, and deliver those weapons via missile technology towards perceived near and medium-distance adversaries. (In the case of Iran, that meant being able to plausibly threaten Israel. In the case of North Korea, that meant being able to threaten both South Korea and Japan, with the added more ambitious idea of lobbing a missile in the direction of the United States).
The world powers involved in both of these stand-offs long ago determined that, on balance, the right approach was containment. Both countries were leaned on heavily to agree to scale back activities that could lead to the creation of nuclear devices. However, given the large gray areas that exist between peaceful and non-peaceful use of technologies that can also be used to create nuclear devices, containment was never likely to prevent progress in both countries towards their possession of nuclear weapons.
However, possession and ability to use are two different scenarios. In neither case has Iran or North Korea demonstrated their ability to launch a nuclear device from within their territory and have it strike the correct pre-determined target. In fact, close to 50% of the North Korea missile tests over the years have been duds.
Robert Farley (one of them experts, so if you are reflexively against reading proper arguments, stop right now and get back to something else), has written recently about what a conflict designed to acheive “regime change” in Iran would look like. Short answer: Nothing good.
The scenario in North Korea is probably more intractable, because of the lack of leverage that the rest of the world has over a country that does not need outside assistance, whose (reluctant) supporter is China. This article explains just how messy the geopolitics in that part of the world has always been, and why the idea that Rocket Man (or whatever juvenile name Donald Trump invented this week can be removed from the scene with a few dozen military strikes is one that is likely to ignite a murderous regional conflict. One perennial suggestion is that the USA could assassinate the North Korean leadership. However, it is far from clear that this would be a constructive action, and there are significant legal and geopolitical obstacles.
Bottom line: these are complex and intractable regional conflicts, and anybody who says “the answer is obvious” is either an uneducated idiot, or somebody who wants a binary solution. In other words, exactly the sort of person who would leap out of the frying pan into the fire.