US government debt now exceeds the nation's entire economic output, signaling a fiscal cliff. JIM LO SCALZO/EPA/Shutterstock

US government debt held by the public just surpassed America’s entire annual economic output — a milestone that signals a rapidly approaching fiscal cliff.

It’s no secret why: Too. Much. Spending.

New data from the Bureau of Economic Analysis pegs publicly held debt at $31.27 trillion, about $50 billion more than GDP for the prior year.

It’s part of an alarming trend — debt growing faster than the economy, with no end in sight.

And it spells big trouble down the road.

In just four years, the debt-to-GDP ratio is on course to break the all-time record of 106%, set just after World War II.

By 2036, it’ll hit 120% — with the deficit at an insane $3.1 trillion.

By 2056, projects the Committee for a Responsible Federal Budget , it’ll soar to an unthinkable 175%.

This path guarantees disaster down the line — unless the nation changes course.

And no, the problem isn’t that Uncle Sam…