No sooner had President Trump finished his United Nations speech on Tuesday than the media had already latched onto its most colorful phrases. Naturally, when a U.S. president refers to Kim Jong Un as "Rocket Man" and threatens to "totally destroy North Korea" if it attacks, that's the part of the speech that everyone is going to dwell on.

In fact, it would surprise us if this doesn't become Trump's "Rocket Man" speech in future history texts.

But Trump did much more than rattle that saber in his speech. Probably his more important contribution was to restore a sense of realism in U.N. diplomats who have in many cases lost sight of how the world really works. His discussion of sovereignty and a U.S. foreign policy that serves U.S. interests might sound like common sense, but it's actually unique and hasn't been heard in quite some time.

You don't have to be a nationalist to appreciate the idea that sovereignty still matters. If banks are where the money is, then sovereign states are where the world's power is and will remain. And with that power comes responsibility to use it as intended. As Trump put it, "All responsible leaders have an obligation to serve their own citizens, and the nation-state remains the best vehicle for elevating the human condition."

The idea that the nation-state had somehow become obsolete has long been on the rise, but in the cold light of day, it is as silly now as it ever was.

The governments that send delegations to the U.N. are empowered by the consent of those they govern, and exist primarily to serve them. And they deserve to be turned out of power if they embrace ulterior motives or adopt incompatible missions in order to satisfy purely ideological goals or the desires of multinational organizations.

Transnational institutions, such as the U.N. or the European Union, are never more than a means to the various ends that their member nations pursue, hopefully in accord with their own citizens' interests.

Thus, Trump is not disrespecting the U.N. when he reserves the right to take action against the direct threat that North Korea poses to the U.S. homeland — a threat the likes of which the U.S. has not seen in nearly 25 years.

Trump was by no means articulating isolationist or unilateralist ideas. Yet he clearly had abandoned Bush- and Obama-era ideas of idealistic military interventions. His sovereignty talk showed that he sees the U.N. as a means, not an end in itself. As an institution, it must not become an obstacle to world peace by protecting a North Korean regime that is putting the entire world at risk with its pointless provocations.

Another way in which Trump's speech distinguishes him from his predecessors is that he did not have to exaggerate any of the threats we face. Recall the theoretical threats to the U.S. that George W. Bush once cited to justify a war. Trump, in contrast, cited perfectly concrete threats whose existence no one can deny. That includes North Korea's and Iran's demonstrated nuclear threat, Islamic State's demonstrated terrorist threat, and the partially realized threat of a regional humanitarian and refugee crisis that is posed by the incompetent and criminal regime of Venezuela's Nicolas Maduro.

Trump made it clear that he sees his job in the realm of foreign policy as using U.S. power on delivering material benefits for U.S. citizens. It's a school of U.S. foreign policy that hasn't been heard from much in the last century, but whose time has surely come.