London (CNN) To inherit one nuclear crisis might look like misfortune, but to develop a second looks like carelessness.

Iran and North Korea are wildly different versions of the same threat, and the White House has taken wildly different approaches to them.

Yes, it is a flawed deal in some respects: It doesn't curtail Iran's regional behavior entirely, or forever. But it does (or at least did) deal with the most dangerous issue -- their pursuit of the bomb -- for about a decade, during which time a lot can improve and hardliners can die out on all sides of a conflict.

Trump, though, saw only the deal's flaws. He listened to a hawkish triumvirate of advisors -- Secretary of State Mike Pompeo , National Security Advisor John Bolton and Israeli leader Benjamin Netanyahu -- believing that tough talk and the threat of tough action might reverse Iran's behavior and weaken the country.

This week has shown that that prediction was only half right.

Iran's economy continues to suffer from US-instigated sanctions and may do so more as petroleum-related waivers expire.

But Iran's response to the oil tanker incident in the Gulf of Oman -- tough rhetoric and the slow rollback of limitations on enrichment of uranium under the nuclear deal -- shows it isn't prepared to back down. Short of friends in a rough neighbourhood, it can't afford to look weak.

And still the US prefers to wield a big stick , rather than focus on diplomacy. Its commander-in-chief says he doesn't really want war and would be willing to talk to Tehran. But sending 1,000 more troops to the region drowns out those calmer noises.

Any US conflict with Iran would be messy, asymmetrical, long-winded and cost America's regional allies dearly, but there is no doubt the US would prevail at what they would regard as an acceptable short-term cost. Their proxies in the region would likely do a lot of the fighting.

But Trump and his team just don't need the hassle -- especially with re-election looming -- so they are making it clear that they don't mean the tough talk to go anywhere nasty. And ultimately, war with Iran would be messy -- but it would not involve a nuclear holocaust. Yet.

On North Korea, meanwhile, President Trump began with "fire and fury," but swiftly realized just how fiery and furious a direct conflict with an unstable nuclear power could get.

There are US troops directly in the firing line of Pyongyang's shells . And Seoul, too, a city of nearly ten million people. Miscalculation with Kim Jong Un could kill millions in hours.His rockets, while clumsy and likely not armed with miniaturized nuclear warheads yet, might one day reach US territory. There is a huge amount more at stake.

So, Trump has opted to largely ignore the urgency of this threat and to focus instead on his ability to bridge the gap through personal charm.

It is unsettling to hear the world's most powerful -- and at times also its most confident -- man discuss the beautiful letters he gets from a dictator whose missiles pose perhaps the gravest threat to the US. But Trump's inner circle knows as clearly as Obama's did that Pyongyang is unlikely to voluntarily disarm unless the economic benefits, along with pressure from China, overwhelm them.

In the meantime, Trump's focus on his personal connection with a strongman thought to have used an anti-aircraft gun to execute his own relatives is buying Pyongyang the time it needs: As each year passes, North Korea continues to develop its arsenal unchecked, getting closer to the point at which Washington will no longer be able to ignore its nuclear reach.

Trump's approach to each of these nuclear conundrums also informs the way the other plays out.

Iran sees that North Korea made a lot of aggressive noise and raced ahead with work on its bomb and ballistic missiles, and that its reward for doing so was a personal summit with Donald Trump.

Tehran can be pretty sure that Trump's offer to answer the Iranian President's phone call will still be on the table when they are better armed.

North Korea sees clearly that the US wants to talk tough with Iran but doesn't really want conflict. But you can't play with the idea of war. It isn't a threat you can make but not mean -- doing so sets in motion a cycle of escalation.

Kim Jong Un will also see something else much more clearly: that Trump doesn't want war with an economically damaged, isolated nation like Iran, who presents little serious threat to the US in direct military conflict.

So we see one crisis in which carefully-constructed diplomacy has been abandoned in favor of hollow military threats, and another in which clumsy and personality-driven diplomacy is being used to try and avoid a stark and inescapable nuclear threat.

Each of Trump's enemies is learning from the experience of the other, and the White House remains none the wiser.