WHEN you talk to Chinese officials lately, it doesn’t take long before they express concern about America’s “rebalancing” of forces — the prospect that we’ll shift more troops from the Middle East, where they are containing instability, to Asia, where they would contain China. My standard reply is that China is worrying about the wrong thing. It is not that we’ll shift our Marines from the Middle East to Asia; it’s that we are going to shift them from the Middle East to San Diego — because we can’t afford to be the world’s policeman much longer, and China will have to fill some of the void.

Good luck, world! It’s been fun hanging with you, but we can’t pay for it anymore — not with all of us baby boomers about to retire with no savings. We have a new strategic doctrine coming: “U.S. foreign policy in the age of Alzheimer’s.” We’ll do what we can afford and forget the rest.

Why do I say that? In part it’s because I spent time this week with the Washington staff of The Jewish Federations of North America, or JFNA, which represents the 155 Jewish community federations across America. They may seem like an unlikely interlocutor for a foreign affairs columnist, but they’re not. Like their counterparts, Catholic Charities and Lutheran Services, these Jewish federations operate nursing homes, hospitals, elder-care programs, meals on wheels, job-training, hospices and family social services in cities across America. And the financial challenges they’re all facing today are profound — as the baby boomers are aging — and so too are the trade-offs we’ll have to make between nursing homes in America and nursery schools in Afghanistan. Unless we get some sustained economic growth, Afghanistan is going to lose.

William Daroff, the director of JFNA’s Washington office, starts with this fact: Since the 2008 economic crisis, annual donations to Jewish federations have been flat, while there has been a sharp increase in demand for services and significant cuts in Medicaid and block grants that help pay for them. “We have people who were donors to our programs five years ago, now knocking on the door to use those same programs” — from people in need of job-training to those in need of help to cover a mortgage payment, said Daroff.