It's not simply that the current US president is deeply unpopular. An average of recent polls sets Joe Biden's approval rating at about 39 per cent, lower than Donald Trump's level at the same point in his presidency.
Nor is it the drubbing he can expect his party to take in November's Midterm elections, thanks to surges in inflation, crime, and turmoil at the US-Mexico border.
Nor is the problem a stalemated Congress. There is still legislation moving forward. Bipartisan passage of a (very) modest gun reform law and possible progress on a slimmed-down plan to spend billions more on infrastructure show that lawmakers haven't exhausted all hope for legislative progress.
But two major stories are now exacerbating America's bitter political divisions, undermining the integrity of US political institutions, igniting fury across America, and setting off alarms of conflicts to come.
Firstly, there are new revelations about Trump's final days as president and the actions of many of his loyalists.
A committee in the US House of Representatives charged with investigating the riot around and inside the US Capitol building on January 6, 2021, has uncovered clear evidence, provided and corroborated in many cases by Trump administration insiders, that the former president attempted to engineer a violent coup following the last presidential election. What he could not accomplish by fraud, he tried to achieve by force.
Yet, no one in Washington has confidence that Trump or his enablers will be held legally accountable for this insurrection in plain sight, and current polls suggest Trump remains the frontrunner to win the Republican Party nomination for president in 2024.
How can Americans expect the rest of the world to take its democracy seriously when 70 per cent of Republican voters do not accept Biden as the legitimately elected president – and many of them say they're prepared to back a man who tried to engineer a coup on live television?
There is good reason to fear that the 2024 presidential election will provoke deadly violence in the United States, and there are large numbers of Americans who will reject the election's legitimacy no matter who wins.
Another loss by Trump, or a Trump-backed candidate, will lead to even louder cries of fraud – and perhaps even to efforts by Trump-friendly state election officials to reverse the election's outcome.
If Trump wins, voters who hate him will insist he won by manipulating the election process and repeatedly lying to the American people. Voters on both sides will accuse those on the other of choosing to live in an alternate reality. Even if primary election voters sweep aside both Trump and Biden in favour of fresh faces, the election legitimacy problem will persist.
But while presidents are elected only for four-year terms, and their critics can always look toward the next election, the judges who sit on the US Supreme Court are nominated and confirmed for lifetime terms, and it's been at least half a century since the US high court has stirred partisan passions as the current court has done over the past few weeks.
Following the controversial (and historically unusual) early press leak of an unfinished draft opinion, the US Supreme Court voted last month to upend precedent and overturn a 50-year-old case that guaranteed abortion rights for American women.
We haven't seen so many Americans lose a court-guaranteed right of this magnitude in 150 years. Two-thirds of Americans oppose the decision.
Most importantly, this decision delivers a seismic political shock that will divide opinion across the nation, and within each of the 50 US states, on one of the most emotive issues in American life.
Polls suggest this decision further undermines confidence in the integrity of the nation's highest court, an institution that has long enjoyed much broader public support than either US presidents or Congress.
Even here, the threat of violence is real. In June, a California man was indicted for trying to murder Supreme Court Justice Brett Kavanaugh. Prosecutors say the man was angry that abortion rights would be denied. The man himself said he feared Kavanaugh would loosen gun laws.
Whatever the case, the January 6 riot has already underlined the risk that those who question the legitimacy of US political institutions will turn to violence.
The Department of Homeland Security has alerted local police and intelligence agencies to unprecedented levels of domestic extremism – from groups on both the right and the left.
A recent study found domestic support for "participating in a political revolution even if it is violent in its ends" is historically high among American young people, at nearly 40 per cent.
With both major parties now led by deeply unpopular men, and so many hot-button political issues triggering so much public anger and so many challenges to the legitimacy of America's political institutions, the world is right to fear that American democracy, which Ronald Reagan once described as a "shining city on a hill," is now under siege from within.
- Ian Bremmer is the president of Eurasia Group and GZERO Media and author The Power of Crisis. He can be found on Facebook and Twitter.
