In some cases, old-fashioned guarantees like the one that prevents a war between North and South Korea will still makes sense. In most cases, however, the US should take the role of "architect" literally, helping regional powers design a system that will function without the US as a full member. This approach that not only makes political sense in the sovereignty sensitive world of Asia and also maintains a maximum degree of flexibility for the US to deploy its own resources as needed around the world.
A little tough love for our allies would help, too.
Around the world, American security guarantees take many forms, some (NATO, South Korea, Taiwan, Japan) explicit and others (Israel, Ukraine, Saudi Arabia, Australia, Colombia) more implicit, for historical and diplomatic reasons.
While America stood like a colossus astride the planet, opaque promises had their advantages. In today's world of WikiLeaks, conspiracy theories and diminished respect for American power, transparency should prevail.
If not, US allies may discover too late they have a paper tiger on their side. Ask the Georgians - many of whom felt the US would come to their aid in 2008 when Russia invaded to support Slavic separatists inside Georgia's borders.
The US may find itself faced with more such dilemmas as nations that formulated their own national security policies based on blanket assurances from Washington stumble into conflicts that America can neither prevent nor afford to fight.
The US should take the lead in encouraging an end to diplomatic anachronisms, such as Japan's constitutional prohibition on spending more than 1 percent of GDP on defense, Israel's "no comment" nuclear arsenal, or the long-running imbalance in US-European NATO defense spending.
In a similar vein, Washington should end the foolish economic embargo of Cuba, which at this point is about the only proof the Castro brothers can point to of their relevance to the modern world. US defense commitments should be in treaty form, and should be debated in Congress.
NATO commitments should be borne according to relative GDP of the member state, and those who failed to spend a mutually agreed percentage of GDP on defense should be suspended from membership.
Allies like South Korean and Japan should pay far more of the costs associated with the US military presence on their soil or, if they see fit, eject American troops and defend themselves.
Taiwan and Israel, perhaps the two nations whose destinies are most tied to American power, should be told that American economic, military and political support will rise and fall according to their commitment to negotiating an end to the destabilizing hostilities that persist with their neighbors.
Simply by osmosis, the US will remain the world's largest economy and dominant military power for at least another few decades. But failing to adjust will hasten decline. The US, by putting enormous pressure on its already strained Treasury, can impersonate a hegemon for another decade or so. If it does this, however, the risk of a real collapse - an uncontrolled unraveling of US power that sparks regional wars and tempts the world's worst actors to take risks - will rise exponentially.
None of this is voluntary or charitable of us - the changes are happening and they are traceable in world economic statistics. Doing this carefully is America's true interest and there's never a better time to be realistic than the present - unless, of course, the present happens to include an American presidential election.