Washington: Stark lines link the Orlando mass murderer Omar Mateen to Thomas Mair, the murderer of British MP Jo Cox, just as dots join the irrational, anti-establishment Brexit movement to a delusional belief that somehow Donald Trump can save America.

I've done my time in the UK and in the US and have often played with the notion that in each country the loonies should have their way.

Britain has always been conflicted about its membership of the European Union, so cease all the mewling and puking, get out of Europe and see what life alone on a rock in the Atlantic is really like; ditto the US – Americans should put a crazy in the White House to help them understand the daily grind of life in la-la land.

In 2012, I had my eye on Newt Gingrich. This time around, Trump, a candidate who thinks that to squint makes him look presidential, will do.

As the Brexiteers and Trumpites head for the polls, there's an eerie similarity to the political noise on both sides of the Atlantic.

There's an increasingly ugly anti-immigrant blather and dog-whistle calls for violence which are pitched to predominantly white, non-capital city voters who have a sense, real as much as imagined, that politicians have betrayed them as wages stagnate and factories and mines that once represented jobs for life are shuttered and mothballed and, particularly in the US, of widespread political and financial corruption.

In both campaigns, voters are told that they are victims of a Washington/Brussels conspiracy, in which politicians, anyone in public office and anyone with a field of expertise that gives them a public voice are up to no good.

In The Spectator, which urges its conservative readership to quit Europe, Alex Massie writes about how the British are conducting themselves, but what he has to say is scarily applicable to the US in the era of Donald Trump:

"Sometimes rhetoric has consequences. If you spend days, weeks, months, years telling people they are under threat, that their country has been stolen from them, that they have been betrayed and sold down the river, that their birthright has been pilfered, that their problem is that they are too slow to realise any of this is happening, that their problem is they are not sufficiently mad as hell, then at some point, in some place, something or someone is going to snap – and then something terrible is going to happen."

There seems to be unanimity among economists and other experts that quitting the EU would inflict serious economic damage on the UK; and that many of the predictions of putting the 'Great' back into Britain are a nonsense - "voodoo wrapped in a Union Jack," as one observer put it. And much of what passes for Trump policy might also be described as voodoo wrapped in the Stars and Stripes.

Attempting the answer the 'why Brexit' question, New York Times columnist Roger Cohen writes: "The answer is that this huge gamble would be taken for the chimera of restored 'sovereignty'. It would reflect petulant nationalism, base bigotry and laughable Little England pretensions…".

And here Cohen segues to a Facebook post by former Times of London foreign editor Martin Fletcher: "Does anyone seriously think the prospect of [post-Brexit] British sanctions would alarm Vladimir Putin, or have persuaded Iran to curtail its nuclear program."

In the UK and the US, much of the debate hinges on demonising the 'other' – in Britain there's a nonsense narrative that the entire population of Turkey is about to descend on Shakespeare's Sceptered Isle; in the US, Trump wants to bar all Muslims from entering the country and kick out 12 million undocumented Hispanic migrants, whose absence would leave Americans with much unpicked lettuce and a lot of unclean toilet bowls.

As with Trump talk, Massie notes an absence of subtlety as he decodes the British barking – "Vote Leave, Britain, or be overrun by brown people. Take control. Take back out country. You know what I mean, don't you: If you want a Turk – or a Syrian – for a neighbour, vote Remain."

Refusing to see the Cox murder in isolation, Polly Toynbee writes in the left-of-centre Guardian: "It occurs against a backdrop of an ugly public mood, in which we have been told to despise the political class, to distrust those who serve, to dehumanise those with whom we do not really identify."

Excluding some who she argues still campaign with honour, she goes on: "but there are others whose recklessness has been open and shocking. I believe they bear responsibility, not for the [Cox] attack itself, but for the current mood: for the inflammatory language, for the finger jabbing, the dog-whistling and the overt racism."

She might as well have been writing of the critiques thrown around by Trump – former GOP nominee, Senator John McCain, was a failure because he was taken prisoner by the Vietnamese; US troops who served in Iraq now were living high on the hog, because they had misappropriated government funds; and President Barack Obama secretly is a traitor.

Could Trump's exploitation of fear be any more outrageous than early this week when he told a rally: "Can you imagine what [Muslim immigrants] will do in large groups, which we're allowing now to come here …There'll be nothing, absolutely nothing, left."

And what's the difference between the incitement to violence in Trump's speeches and those of Nigel Farage, a leader in the pro-Brexit movement, when he says: "If people feel they have lost control completely…if people feel that voting doesn't change anything, then violence is the next step".

As Trump makes off with their presidential nomination, some Republican leaders make their own dog whistle calls to voters – not that he should not be their candidate but a bizarre assurance that there are sufficient checks and balances in the system to keep a wayward President Trump on a leash. Any sense of principle gets hurled under the bus of winning the White House.

There is a singular disappointment in how all this plays out. On both sides of the pond, there are clear signs that the system is in bad need of recalibration and repair. In London, the polls are tight but the bookies are tipping that Britons will vote to hang-in with the EU; and in the US, each new day of the Trump campaign points to a likely Clinton presidency.

In both cases, that's a pity, because those likely outcomes would be read as a vote for the status quo, for more of the political negligence that creates an environment in which something or someone snaps.

It could be the murder of a single MP in Britain; or another massacre in the US.

The art of the anti-establishment dog whistle is to create a sense of victimhood. In the US a parade of mass murderers shows how effective it can be – and that's the line that joins Mair and Mateen.

Mair had his neo-Nazi connections. And just as some excuse Mair as mentally unstable, Mateen is portrayed as an angry Muslim who grew up in a house ruled by his bonkers, Afghan father.

But Mateen also was a product of an American political and entertainment culture that says hugely destructive weapons are a sanctioned right – and in the absence of evidence to the contrary, it likely will emerge that his invocation of the name of the so-called Islamic State was a late but calculated effort to drape his bloody departure in added fear and loathing, perhaps to make himself look and sound scarier than a pissant who couldn't cope with being gay.

When he gave a commencement address at Stanford University, the historical documentary maker Ken Burns got stuck into Trump – but Britons would know the Trump equivalents in their midst.

Here's what Burns said: "I recognise this type. He emerges everywhere in all eras…[nurturing] an incipient proto-fascism, a nativist anti-immigrant Know Nothingism…a political paranoia that, predictably, points fingers, always making the other wrong."

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