Not to diminish the capacity of the British for public disorder, but there is something darkly comic about watching, split-screen style, the contrast between the UK and US in the run-up to their general elections. While in the US, the former president and frontrunner becomes a convicted felon who shares videos referring to the possibility of establishing a “unified reich”, the UK’s prime minister enjoys a drink in a cafe by the river as a boatload of Lib Dems, holding placards and waving vaguely sardonically, gently bobs down the river behind him. In the US, the threat of political violence becomes ever more present, with a movie imagining civil war in the republic topping the box office and Trump facing further charges of election interference. In Britain, a news alert at the top of the week announces: “Drink thrown at Nigel Farage during campaign visit to Clacton.” (It was a banana milkshake, and of course it was Clacton. Where else could it have been?) Britain has experienced sustained political violence more recently than the US, as British people love to point out to Irish Americans fondly valorising ye olde IRA. But held up against what’s happening in in the US, and for all the Tory party’s awfulness of the past 14 years, Rishi Sunak’s appeal to the British electorate on Tuesday night made him look about as threatening as a Beatrix Potter villain. This is not how things are in the US, where a week on from Trump’s historic felony conviction, the fallout couldn’t be worse. Any sense of triumph experienced last week at the reading out of 34 guilty counts against Trump was curtailed, instantly and viscerally, by the verdict’s implications. This was not the same moment of giddy jubilance as when Trump was found liable for sexually assaulting and defaming E Jean Carroll (twice) and ordered to pay her $83.3m. But that was the civil courts. In Judge Merchan’s court last Thursday, Trump became a convicted felon – a turn of events that, no matter how keenly we might have sought and anticipated it, seemed at the moment of reckoning to be a truly shocking and frightening development. We talk about Trump as a figure who, over the past eight years, has expanded the Overton window to a degree no one imagined possible. Last week, it stretched to accommodate the prospect of a man found guilty of a hush-money plot to influence a previous election possibly winning the next one. And accommodate is the word. For anyone clinging to the delusion that a criminal conviction would, finally, trigger a grain of conscience in Republican high command, the disappointment was swift and unsettling. For a moment, oddly, only Trump himself seemed deflated. Whether as a result of age (he turns 78 next week), his recent weight loss or the stress finally catching up with him, after the verdict he looked hollow-faced, like an empty espadrille peeping out from a fringe of rush matting. It hardly mattered. If Trump was quiet, his proxies in the form of Mitch McConnell, Susan Collins and a slew of other Republican leaders leapt, shamefully, to his defence. Susan B Glasser in the New Yorker handily collated the worst of these, from a tweet by Nick Ayers, the former Trump White House staffer, who wrote “Kangaroo court. Banana republic”, to the Republican senator for Kansas, Roger Marshall, calling the verdict “the most egregious miscarriage of justice in our nation’s history”. Marco Rubio, making up in hyperbole for what he lacks, as Trump himself has pointed out, in stature, claimed that “the public spectacle of political show trials has come to America”. And there it was: criminality sanctioned and embraced at the highest levels of government, with the implicit invitation to act accordingly to all who follow him. And let’s not forget Nikki Haley. When she was running against Trump during the primaries, Haley threw some of the toughest criticism of any Republican his way. Well, that was then. The day after Trump’s defence team rested their case, up popped the former governor of South Carolina to confirm that, come November, she would be voting for a man she once called “diminished” and “unhinged”. In response to which, I find myself regressing to childishness. How could you?! Are you out of your mind? When all of this ends in Trump seizing an illegal third term and passing legislation to enable the deployment of US troops on domestic soil, what will you put in your press release? Or, at that point, will you be too busy angling for secretary of defense? We know where undermining public faith in a country’s justice system can lead. And we know that Trump will do anything to secure his own victory. Now we know something else, too. When the guilty verdict rang out 34 times last week, my heart sank and an odd thought – in keeping with all the other absurdities thrown up by Trump – came to mind. Better that he had been found not guilty than convicted and the quiet part said out loud: that there is no line. That no one on his own side will do anything to stop him. Emma Brockes is a Guardian columnist