A cross-border effort is under way to stabilize the Japanese yen, and Americans have a real stake in whether it works.

• The US, Japan, and South Korea are coordinating to prop up the falling yen.
• The US is involved because a yen collapse could force Japan to dump its large pile of US government bonds.
• If Japan sells those bonds, US interest rates would jump, raising borrowing costs for people and companies.
• Higher rates would also fuel more inflation — the opposite of what the Fed, the US government, and Japan all want.

Outlook: Expect continued joint support for the yen to keep it from sliding further and dragging US rates up with it.