Washington's different treatments of Iran and North Korea have been marked since US President Donald Trump withdrew the US from the international pact over Iran's nuclear programme.
Iran has since faced diplomatic, military and economic pressure even as Trump has wooed Kim with summits and talks.
In recent months the US and Iran have engaged in simmering skirmishes that Trump suddenly brought to the boil with the assassination by drone of General Qassem Soleimani in Iraq.
While the US had previously dispatched non-state extremist leaders waging jihad such as al-Qaeda's Osama bin Laden and Abu Bakr al-Baghdadi of Isis, Soleimani was different – a senior figure in Tehran's regime, part of a sovereign state.
Foreign Policy magazine now ominously asks: "Is preemptive assassination the new Trump doctrine?"
Many US officials and analysts cheered Soleimani's death, saying he deserved it as a "bad guy". Others pointed out that if Soleimani's killing was justified by his actions where did that leave the likes of North Korea's Kim?
And what about future consequences?
Even though an initial standoff has passed, nothing has essentially changed in the US-Iranian confrontation.
The chances of further rounds of conflict, casualties and miscalculations are high. Tragedy has already occurred with Iran's "mistaken" downing of a civilian plane.
Unlike North Korea, Iran does not have nuclear weapons. Like Muammar Gaddafi's Libya, Iran struck a nuclear non-proliferation deal with the US.
A state with only conventional military capability is an easier target. Saddam Hussein's Iraq was unable to deter the 2003 US invasion.
US foreign policy expert Suzanne DiMaggio tweeted that the North Koreans will begin to cite Soleimani as a "cautionary tale" alongside Gaddafi and Saddam.
"The NKs have been paying close attention to the demise of the Iran nuclear deal ... A key lesson is: Even if you're honouring your commitments, the US can still violate the terms of an agreement and take measures to destroy your economy."
It all suggests that the slim likelihood of North Korea giving up its nuclear weapons is now nil.