Around the world, the shock of last week's assault on Capitol Hill brought into sharp focus a question that has been smoldering for four years among America's allies and adversaries.

"And again the doubt," wrote Emma Riverola in El Periódico de Catalunya, a Barcelona, Spain, daily, in painfully graphic terms. "Is this just a final burst of pus? Or has the infection spread, now threatening to cause a sepsis of the entire system?"

Was President Donald Trump an aberration or the ominous onset of decline in the world's premier democracy? The question echoed in democracies beset in recent years by populist movements nurtured by the same blend of far-right nationalism and blue-collar grievances as Trump's following.

For Richard Haass, a long-serving diplomat and the president of the Council on Foreign Relations, it was nothing less than the end of an era.

"We are seeing images that I never imagined we would see in this country — in some other capital, yes, but not here," he tweeted. "No one in the world is likely to see, respect, fear or depend on us in the same way again. If the post-American era has a start date, it is almost certainly today."

The shock will wear off. The inauguration of a president more in tune with the democratic world's perception of an American leader will be a strong demonstration of the resilience of American democracy, and President-elect Joe Biden has promised rapid action to undo the worst damage done abroad by Trump. The raging coronavirus pandemic will resume its proper place at the top of the global agenda.

But the depth and anguish of the world's reaction indicate that something very basic in America's relationship with the world has been broken. It will take more than Biden's insisting that "we're better than that" to convince democratic friends or dictatorial adversaries that the assault on the heart of American democracy by Trump's zealous followers was just a temporary malfunction.