When President Obama jumped the constitutional fence this month and took immigration policy largely into his own hands, he set off a newly raucous debate covering every facet of the issue — except maybe the most important one.

Plenty of attention is being paid to the separation-of-powers dispute. The tricky politics of immigration for all sides is well-analyzed. Thoughtful discussions abound on the economic costs and benefits of immigration along with heartfelt musings about fairness for would-be legal immigrants and humanitarian considerations for millions of illegal immigrants already living, working and raising families here.

These are all important matters, due the attention they're getting.

But what's odd is how seldom and how slightly America's immigration dilemma seems to get discussed as, at bottom, a foreign-policy problem — and one that may have light to shed on the nation's broader soul-searching about the role it plays in the world.

Say what you will about the assertive foreign policies of Russia, or China, or Israel, or Iran. Different as may be their circumstances and intentions, they all have one foreign-­policy habit in common — a clear focus on their immediate surroundings. They concentrate on influencing events in what they see as favorable directions in nations and regions right next door.

America's gaze, by contrast, usually seems riveted on the other side of the world. The rise of ISIL has frustrated Obama's determination to disentangle the U.S. militarily from the Middle East. But his plan was to promptly "pivot to Asia" — to refocus on a different set of international tensions and troubles 10,000 miles away from home.

Whether America's unique global presence is critical to world peace or an outdated burden we should gracefully surrender is a complex debate. But the chronic U.S. immigration problem suggests that a set of international tensions and troubles in our own back yard may need to move up on our priority list.

This is an argument that geopolitical analyst Robert D. Kaplan made forcefully in his eye-opening 2012 book, "The Revenge of Geography." Basically, Kaplan's analysis suggests that America faces no more critical foreign-policy challenge in the decades ahead than finding ways to help Mexico and Central America become more prosperous and stable.

No international frontier in the world, Kaplan notes, marks a more stark economic contrast between rich and poor than the U.S.-Mexican border. Beyond lies Central America, with, in many places, even deeper distress. Witness the surge of unaccompanied immigrant children, often from Honduras, El Salvador and Guatemala, that made so much news this summer.

Such troubles in the neighborhood pose dangers for America that could grow if the troubles do — or at minimum stunt American opportunities. And it is frankly hard to imagine a lasting and acceptable remedy to the flow of illicit immigration so long as America's 2,000-mile southwestern border — devoid of insurmountable natural obstacles — separates this rich and open society from a fast-growing population of hundreds of millions suffering poverty, crime, corruption and dysfunctional governance. The incentives to find a way north are and will remain overwhelming.

Even if Berlin Wall-style "border security" could be established, and stomached over time — all doubtful — America's economic interests and safety would surely be better served by vigorous efforts to help put our "neighborhood" on track toward a better future.

Yet America's relative lack of interest in conditions to its south is striking. The brutal Syrian civil war and the atrocities of ISIL and others in the Mideast rightly stir American passions and inspire intense media interest. But tens of thousands have died in recent years in Mexico's "Drug War" between the government and the cartels (and among rival cartels) without inspiring comparable American interest and concern.

Just two months ago, 43 protesting students were reportedly abducted and massacred by drug lords in Iguala, south of Mexico City, with the apparent cooperation of some local officials. The human-rights outrage has made the U.S. news, of course, but one senses it might have been a bigger story had it happened several continents away.

It isn't clear — at least not to me — exactly what a foreign-policy pivot to our own back yard would look like. Seizing every opportunity to spur regional progress through trade and economic policies would obviously be part of it. Cooperative drug-policy reform might be a part, along with whatever law enforcement, intelligence and even military cooperation could be useful. No doubt rational, comprehensive immigration reform itself could help, freeing up the efficient movement of labor and investment across borders.

Above all, more attention, more energy and more focus at the highest levels on the issues of our own part of the world seems only sensible and overdue — not just as part of the effort to fix a broken immigration system, but as part of reconsidering America's ambitions and capacities in a changing world.

D.J. Tice is at Doug.Tice@startribune.com.