Jon Stewart and Barack Obama are men of a similar age with, on some days, a similar role. Sometimes it falls to both of them to help their fellow Americans digest what’s happening around them, to make sense of it. Yesterday it was the murder by a white supremacist of nine black churchgoers in Charleston, South Carolina.

The TV host did something unusual, dispensing with his usual gag-packed opening to deliver a joke-free monologue. Obama, by contrast, did something that has become all too usual, delivering what is now a rhetorical genre of its own: the presidential post-massacre speech. “I’ve had to make statements like this too many times,” he said. By one count, it was the 14th time he had had to speak in such a way after such a mass shooting.

Stewart’s emphasis was on America’s enduring struggle over race. Obama chose to focus on the country’s equally stubborn problem with guns. But what was striking was that on both questions – what my colleague Gary Younge rightly calls America’s “twin pathologies” – both the presenter and the president struck the same tone. They matched each other in weary resignation.

Stewart said Americans had been forced to peer into a “gaping racial wound that will not heal”. Then, with a comic’s timing, he added that he was confident that “by staring into that and seeing it for what it is … we still won’t do jack shit”.

For his part, Obama began with a declaration that “it is in our power to do something about” the guns epidemic. But then he dampened any expectation of action. “I say that recognising the politics in this town foreclose a lot of those avenues right now.” Mindful of a hostile Congress that has thwarted him at every turn, all he could promise was that America would, “at some point”, have “to come to grips with” the issue of gun violence, and “shift how we think about” it.

You can see why both men – nearing the end of their terms of office – have given up hope that change is on its way. When it comes to both race and guns, there have been episodes so shocking that people assumed action was bound to follow. And yet the brutality, especially police brutality, shown towards black Americans – those doing nothing more threatening than walking or breathing or swimming or praying – goes on.

When in 2012 a 20-year-old man walked into Sandy Hook elementary school in Newtown, Connecticut, killing 20 children and six adults, many assumed this would finally expose the limits of American indulgence of gun rights. Obama declared enough was enough and proposed a raft of gun control measures. They seemed to be making progress until the National Rifle Association got busy, pressuring wavering senators facing tough re-election battles, and the effort was crushed.

Race and guns are the birth defects of the American republic, their distorting presence visible in the US constitution itself. The very first article of that founding document spelled out its view that those “bound to service for a term of years” – slaves – would count as “three fifths of all other Persons”. Meanwhile, the second amendment enshrines “the right of the people to keep and bear Arms”.

The three-fifths rule was eventually discarded, but the legacy of slavery hangs heavy. In South Carolina the flag of the slave-owning Confederacy still flies. The church where those worshippers were gunned down was on Calhoun Street, named in honour of a luminary of 19th-century white supremacism. As for guns, a rule written in the age of the musket, designed to protect an infant republic from the return of King George’s redcoats, still holds – allowing a 21-year-old bent on provoking a race war easy, legal access to a weapon that lets him commit what, in a different context, would be called an act of terror.

A rule written in the musket age, to protect an infant republic from the return of King George’s redcoats, still holds

The result is paralysis and a desperate fatalism. The paradoxes are obvious. America, the land of restless innovation, is shackled to its past. The United States sees its own wounds and cannot heal them, its hands tied by a constitution that in almost every other respect is a manifesto for liberation.

This is obviously a catastrophe for Americans, and not only because of the damage guns and racism inflict both separately and when they collide, as they did so devastatingly in Charleston. It also feeds a corrosive cynicism. Americans are already sceptical of their democracy, which can seem more like a dynastic plutocracy, a perennial battle of the House of Bush against the House of Clinton, bankrolled by unseen corporate giants. But when they see a US president apparently impotent in the face of the gun menace, what are they meant to think of their own power to change things for the better?

Americans like to tell themselves anything is possible, that their destiny is in their own hands. Politicians describe the country as “this great experiment in self-government”, insisting they can make America anew if they want to. Yet the persistence of arms and racism and armed racism suggests that the people are, in important ways, powerless: a nation still ruled by its ancestors; a nation that has forgotten the wisdom of one of its greatest revolutionaries, Thomas Paine, who understood that “government is for the living, and not for the dead; it is the living only that has any right in it”.

All this matters beyond America too. US influence in the world does not rest solely on its wealth and military might. It also requires America to be admired. As Bill Clinton said five years after the Iraq invasion: “People the world over have always been more impressed by the power of our example than by the example of our power.”

Every one of these mass killings, or police shootings of innocent black men and women, undermines that example. It makes America look like a basket case, a country that seems to think it’s normal for a toddler to find a gun in his mother’s purse and accidentally shoot himself dead, a country that saw 12,600 of its people shot dead last year and believes itself incapable of doing anything about it.

To change will mean looking to the rest of the world, and recognising that, as Obama said, most “advanced countries” do not have this problem. It will require a reckoning with the circumstances of America’s birth – and the courage to say that the US is not the country it was more than two centuries ago, and can no longer be bound by those rules: that it has changed – and that it can be so much better.