Public Debt: After repeated warnings from government finance officials around the world, the exploding U.S. debt has suddenly become a major issue for foreign buyers. Maybe it's time we paid attention, too.

Worried about having too much U.S. debt on their books, a number of countries are cutting their holdings of American government and corporate bonds.

According to the U.S. Treasury, foreign holdings of T-bills plunged $53 billion in December — a record. More than $34 billion of it was dumped by China, which fell to No. 2 among holders of U.S. debt. Regaining the top spot was Japan, with $768.8 billion. All told, foreigners hold $2.37 trillion of U.S. government securities.

One month does not a long-term trend make. Yet, it's worrisome that as the U.S. is printing record amounts of new debt, the main buyers are showing a lack of appetite for what we're serving .

In recent months, Chinese officials have made it clear they're concerned about the size of their U.S. debt portfolio and wanted to shrink it. They're doing that now, with a vengeance. Others are doing the same, though not on the same scale.

But isn't it just a lot of accounting, moving dollars from one national ledger to the other? In a sense, yes. But remember: When we sell our debt, the interest is determined by the demand for that debt. When demand is low, issuers have to offer higher interest rates to lure buyers. That's starting to happen now.

Our supply of debt threatens to overwhelm the demand for it. In the next 10 years, according to the Congressional Budget Office, the U.S. could add as much as $13 trillion to its debt load — an unparalleled expansion, roughly equal to a year of our current GDP.

With this year's deficit expected to come in at $1.56 trillion and next year's at $1.4 trillion, the debt is piling up fast. We never worried too much about it, as long as it stayed a minor part of the U.S. economy. Some debt can even be healthy.

But in recent years, our debt-to-GDP ratio has exploded. Today, it's 94% of GDP, up from 83% in 2009 and a little bit more than 60% two years ago. By 2020, it will be well over 100%, according to government estimates. And it will soon take over our budget.

If foreigners ever decide en masse they don't want to hold U.S. debts — kind of like beleaguered Greece today — the U.S. economy would suffer from rising interest rates, a plunging currency and rampant inflation. We'd survive, but not without a lot of pain.

Those who think the U.S. is special and the elementary rules of finance and economics don't apply to us are wrong. And, as the saying goes, when the U.S. sneezes, the rest of the world catches a cold.

We can fix this problem now. But it'll take discipline.

The surge in debt and deficits over the next 10 years is due almost entirely to out-of-control spending. As the Heritage Foundation's Brian Riedl notes, out of $45 trillion in total U.S. spending, we'll spend $26 trillion over the next 10 years on entitlements and interest payments alone. We need to bring spending under control.

But even spending control won't be enough. To get America growing again, the government needs to stop using the tax code to punish savings and investment. If not, we'll soon find our debts have become fiscal leg irons, and we, their prisoners.