US Debt Crosses $40 Trillion Mark: What Does It Mean for Markets and the Global Economy?

The United States government's debt has crossed the $40 trillion mark, bringing renewed attention to the country's rising borrowing needs and long-term fiscal challenges.

The increase has been building for years. When Donald Trump took office in January 2017, US federal debt was around $20 trillion. By the time Joe Biden became president in January 2021, it had climbed to nearly $28 trillion. Since then, debt has continued to rise, crossing the $40 trillion threshold in 2026, meaning the US debt burden has roughly doubled in less than a decade.

The rise does not come from one single factor. A combination of tax cuts, higher government spending, pandemic-related support measures, infrastructure investments and rising interest costs have all played a role in getting here.
For investors, the bigger question is not just the size of the debt but how it affects interest rates, bond markets, the US dollar and global capital flows.

How Did US Debt Double Over the Last Decade?

The US has been running budget deficits for several years now, meaning government spending has regularly exceeded what it earns from taxes and other sources.

The first Trump administration implemented the Tax Cuts and Jobs Act in 2017, which lowered the corporate tax rate from 35% to 21% and decreased personal income tax rates. The proponents claimed that low taxes would promote investments and growth, yet the government lost some of its funds.

The bigger jump came during the COVID-19 pandemic. Between March 2020 and March 2021, the US government introduced large relief packages worth around $5 trillion to support households, businesses and state governments during the economic shutdown. These measures helped cushion the impact of the crisis but also resulted in a sharp increase in government borrowing.

In the period of Joe Biden’s presidency, there was high spending through programs like the $1.2 trillion Infrastructure Investment and Jobs Act, the $280 billion CHIPS and Science Act for semiconductors production, and the $370 billion Inflation Reduction Act that concentrated on energy and climate change investments. There was also high defense spending during his presidency.

At the same time, interest payments on existing debt became a larger burden as borrowing costs increased.

Higher Interest Rates Make Debt More Expensive

However, besides the amount borrowed, another reason why there have been worries regarding debt in the USA is because of the cost associated with repaying that debt. Interest rates have been significantly raised in the USA since 2022 due to high levels of inflation. The Federal Reserve raised rates from near zero in early 2022 to 5.25%-5.50% by July 2023 
This means that the USA has been paying higher interest rates on new debts and refinanced debts.

According to the Congressional Budget Office, the amount of net interest paid on US debt went past $800 billion during FY24. This has become one of the fastest growing budget items for the federal government. Higher interest costs can hold back the government's ability to spend on other priorities.

A larger interest burden also means that future policy decisions may become more difficult, especially if economic growth slows or borrowing costs remain high for longer.

Why Global Investors Track US Debt Closely?

The US dollar plays a central role in the global financial system, and US Treasury bonds are widely held by governments, institutions and investors around the world. There is an estimate that the foreign investors own about $8 trillion worth of the US Treasury securities, making the United States Government bonds an important part of the global financial markets.

Given their position, the United States has traditionally enjoyed relatively cheap borrowing compared to many other countries. Nevertheless, the further increase in debt can affect the expectations of the investors concerning the future borrowing.

If investors demand higher returns to hold US government bonds, Treasury yields could rise. Higher US bond yields often have a ripple effect across global markets, influencing currency movements, equity valuations and investment flows.

For emerging markets like India, changes in US yields and dollar movements are closely watched. Higher US rates can make dollar assets more attractive and may pull foreign investor flows away from emerging economies.

Is the US Debt Level Sustainable?

There is no simple answer to whether a $40 trillion debt burden is manageable. Much depends on economic growth, inflation, interest rates and future government policies.

The US ratio of gross debt to GDP is now more than 120%, which underlines just how high the level of borrowing is relative to the size of the economy.

Those who support greater borrowing argue that debts can stay under control if the economy develops quickly enough and borrowed funds are put to productive use. Critics on the other hand point out that persistent deficits can put growing pressure on government budgets over time.

The US budget deficit was around $1.8 trillion in FY24, showing that government spending continues to exceed revenue by a wide margin.  International organisations including the IMF have repeatedly stressed the importance of maintaining sustainable fiscal policies, especially for large economies with rising debt levels.

That said, the effect of debt plays out differently for the US given that the dollar is the world's leading reserve currency. This provides a certain level of flexibility that other nations simply do not have access to.

What Should Investors Watch Next?

Markets will closely follow US government borrowing plans, Federal Reserve policy and movements in Treasury yields.
Higher inflation, borrowing needs that exceed expectations, or changes in the fiscal policy can affect interest rates expectations. They can also have a bearing on the world’s stock markets, foreign exchange markets, and general market psychology.

For Indian investors, what happens in the US bond market may have a bigger effect due to global liquidity considerations as well as foreign investments. Foreign investors in the CY24 sold Indian stocks for more than ₹1.2 lakh crore.

Conclusion

The US hitting the $40 trillion mark is a reflection of how much the country's expenditures have grown over the years alongside persistent budget deficits. US federal debt has gone up by over $20 trillion since 2017 due to a range of economic and policy factors.

Despite the advantage the US holds as the issuer of the world's reserve currency and the strength of its financial markets, the rising cost of interest remains a concern that is unlikely to go away on its own.

For markets, the focus will remain on how effectively the US manages its debt while balancing economic growth, inflation control and fiscal responsibility.