The selloff in U.S. Treasurys has captured global attention, but bond markets overseas have been getting hit even harder.

The jump in U.S. borrowing costs-and Treasury Secretary Scott Bessent's intervention to bring them back down-has shone a spotlight not just on America's growing debt problem but the world's.

Global debt has surpassed $350 trillion, according to the Institute of International Finance, or about 305% of global gross domestic product. Governments in advanced economies alone are expected to borrow $18 trillion this year, according to the OECD, and are increasingly competing for buyers with stocks and bonds issued by U.S. tech companies.

While global bond yields have eased this week, they remain near their highest level in more than a decade in several countries. Countries with large debt burdens-France, Italy, the U.K., Japan-have come under the heaviest pressure in recent months.

France's benchmark 10-year yield has risen around half a percentage point since the end of June, while Italy's is up almost as much. The U.S. 10-year Treasury yield meanwhile, has risen about 0.2 percentage point.

"People are testing the waters of what the U.S. should pay [to borrow], but then they look to other countries like France and there are all these fragilities," said Ludovic Subran, chief investment officer of German insurer Allianz. "Everybody is testing which countries will yield first to bond vigilantes' pressure," he said, referring to the idea that bond investors hold profligate borrowers to account.

Moves in the U.S. Treasury market often have global spillovers. U.S. government bonds remain the backbone of the global financial system and set the baseline for a range of investments.

But other factors have exacerbated the selloff: inflation worries driven by the continuing war in Iran and questions over central banks' willingness to fight it; political volatility; and a retreat by once-reliable bond buyers like pension funds and insurers in many countries.

Here's a breakdown of the forces fueling the overseas rout.

Inflation fears make a comeback

Many economists thought inflation sparked by the war in Iran was subsiding, but concerns are building once again in Europe and Asia, two continents heavily dependent on energy imports.

This week, natural-gas prices in Europe rose to their highest level in more than three years. European and Asian buyers are locked in a bidding war over constrained supplies from the Middle East. European countries in particular are under pressure to fill up gas storage ahead of the winter.

The supply crunch has revived memories of 2022, when Europe scrambled for gas after Russia cut off supply in response to the war in Ukraine, according to Tomasz Wieladek, chief European macro strategist at T. Rowe Price. The European Central Bank embarked on an aggressive rate-hiking campaign.

"The market has some muscle memory," he said. "Last time around, the gas price...was the key canary in the coal mine for higher inflation."

Yields on government bonds are heavily influenced by investors' expectations for short-term interest rates set by central banks. Due to inflation concerns, investors are now pricing in about one-and-a-half rate increases from the ECB this year, compared with one earlier in August.

France's fiscal woes

France has been in the eye of the storm in recent weeks. President Emmanuel Macron's government has struggled for years to rein in spending. The budget deficit is expected to remain at about 5% of GDP this year, and economic growth remains tepid.

Investors are on edge about next year's election to succeed Macron. New polling has cemented populist leader Marine Le Pen's front-runner status. Investors question whether she will commit to curbing spending.

France now pays more to borrow than almost any other major European country, including Greece and Italy. A measure of the stress: France has to pay about 0.85 percentage point in additional interest than Germany to issue a 10-year bond, near its widest point in years.

Guilhem Savry, head of equity and fixed-income strategy at Edmond de Rothschild, thinks that premium will top a full percentage point as the election nears.

"France's debt is not sustainable in the long term, and the market is starting to understand," he said. "The future is very dark for France."

Japan's inflation problem

Japan's bond yields have surged this year, as a decadeslong stretch of deflation recedes further into the background. Headline inflation is approaching 2% in Japan, but the Bank of Japan has raised rates just once this year, to 1%. The central bank's reluctance to raise interest rates has pressured the Japanese yen, prompting a rare U.S.-Japan joint intervention to prop up the currency.

Many investors believe the BOJ is on the cusp of shifting to a more aggressive stance, with markets now pricing in a rate increase by October.

Some investors are also concerned about Prime Minister Sanae Takaichi's spending proposals, which include plans to cut the consumption tax and raise defense investment. Japan has been whittling down its debt load-which stands at about 200% of GDP-and is running one of the smallest budget deficits among major economies.

But interest payments on debt are mounting as the jump in borrowing costs makes new debt more expensive. Debt-servicing payments are reportedly expected to cost Japan roughly $230 billion in its next fiscal year, up 17%. Japan has historically offset much of what it pays on debt with income it earns on its enormous overseas investments, but that advantage is waning as domestic borrowing costs climb.

U.K.'s budget worries

The U.K. bond market has been particularly sensitive to global bond market frictions since 2022, when then-Prime Minister Liz Truss shocked investors with a plan for unfunded tax cuts.

Her successors have tried to rebuild investors' trust by sticking to strict budgeting rules, but investors remain anxious about the U.K.'s debt path. Like other European countries, the U.K. has also been facing a shift in demand, as pension funds that used to vacuum up long-term government bonds shift into other investments.

Rising yields are making new Prime Minister Andy Burnham's ambitious plans for reviving home-building and investment harder to achieve. He has sought to reassure investors by pledging to stick to the U.K.'s budget rules. A key test will come this fall when his government presents its first budget. The recent rise in borrowing costs will cost the U.K. about $10 billion, according to Société Générale, limiting his room for new spending.