Is America heading into another Global Financial Crisis? Well, the comparison is tempting. In 2007, leverage had spread through mortgages, banks and opaque credit products before the system cracked. In 2026, leverage is sitting somewhere very different: on the public balance sheet.

US gross national debt passed US$40 trillion in August 2026 and stood at about US$40.1 trillion by 3 September. Meanwhile, the Congressional Budget Office (CBO) projects a fiscal 2026 deficit of US$1.9 trillion, or 5.8% of gross domestic product (GDP).

That does not make 2026 another GFC but it does raise a different question: what happens when the world's benchmark bond market has to absorb increasingly large borrowing requirements while inflation is still making life difficult for central banks?

2007 vs 2026

The similarities are real, but the breaking mechanisms are not.

While the GFC was fundamentally a credit and banking crisis, today's concern means US Treasuries remain the benchmark sovereign asset, but investors still have to decide what yield compensates them for inflation, duration and the volume of debt coming to market.

That difference matters. This is not subprime with a new label; it is a different strain on the same global financial plumbing.

Why US$40 trillion matters

The headline debt figure is eye-catching, but the flow numbers tell more of the story.

CBO expects the federal deficit to reach US$1.9 trillion in 2026, well above its 50-year average relative to GDP. Debt held by the public is projected at 101% of GDP, while net interest outlays are expected to exceed US$1 trillion this year and continue rising over the next decade.

That creates a straightforward mechanical dynamic:

We have already seen glimpses of that upward repricing. The US 10-year Treasury yield briefly crossed 5% on 14 September, while official Treasury data put the 30-year yield at 5.35% on 11 September. Those are not crisis signals by themselves, rather they are market clearing prices. The question is what happens if elevated yields become persistent.

When the deficit starts calling the shots

This is where the term fiscal dominance enters the conversation.

The Bank for International Settlements (BIS) defines fiscal dominance as a situation where fiscal constraints begin limiting a central bank's ability to tighten monetary policy. In its more severe form, higher borrowing costs increase sovereign financing pressure enough to compromise monetary policy independence.

The US is not automatically in fiscal dominance simply because national debt has crossed US$40 trillion. That distinction is essential. The underlying risk is that persistent deficits, higher refinancing costs, and sticky inflation increasingly pull fiscal and monetary policy in opposite directions:

• Cut rates too early, and inflation risks reaccelerating.
• Keep monetary conditions tight for longer, and government interest outlays compound as debt rolls over.

Four numbers that matter

Sovereign debt stress does not need to resemble a 2007-style bank run. It can express itself gradually through primary and secondary Treasury market metrics.

Signals worth tracking, without reading a signal too hard

The ripple that reaches Aussie mortgages

Australia does not import US Treasury yields on a strict one-for-one basis, but global capital markets remain interconnected.

The Reserve Bank of Australia (RBA) noted in August that rising offshore government bond yields, particularly in the US, contributed to shifts in Australian yield differentials and the Australian dollar (AUD). Concurrently, Australian commercial bank funding costs remain governed by the domestic cash rate, customer deposits, wholesale debt markets, and short-term reference rates like the Bank Bill Swap Rate (BBSW).

The bottom line

Another GFC? Not in the 2007 structural sense. The debt resides on public balance sheets, the underlying collateral is sovereign rather than subprime mortgages, and the transmission channels operate through yields rather than bank liquidity freezes.

The primary risk is not toxic assets hiding on private bank balance sheets. It is evaluating how much sovereign debt global markets can smoothly digest, what yield investors demand to hold duration, and how much operational flexibility central banks retain if inflation remains stubborn.

Different crisis. Different plumbing. Same reason to keep a close watch on the pipes.