Trump is certainly the more repellent, with his racism, sexism and mockery of people with disabilities. I will never forget asking an elderly black woman in West Virginia about her new president, and seeing her eyes fill with tears as she told me she was so upset she could not watch the news for 10 days after the election. His vile behavior toward refugees demeans a great nation founded on immigration. It is also horrific to see someone in the White House use white supremacists as political props and transgender people as pawns.
However painful those Trumpian traits might be, though, their potency will fade once this disruptive figure has left office. The president's nastiness to his fellow citizens is also clearly energising the opposition. More damaging in the long term is the way that Trump's endless lying degrades the presidency in an era when politics is being transformed by technology and when public cynicism is growing. His abuse of journalism and embrace of despots are already having serious global consequences.
Yet even if Trump wins a second term, Brexit is the more severe act of national self-harm - with two caveats. First, it is always possible Trump does something so ill-conceived that he ends up starting a real war, not a trade war. Second, for all the robustness of the United States' constitutional checks and balances, his impact on politics might be irredeemable if he is succeeded by another infantile attention-seeker.
But at least Trump will one day depart the stage. Britain, by contrast, is in such a humiliating mess that it still has no clear idea how it will leave the European Union six weeks from now. Ships laden with goods have already set off from Asian ports, their owners uncertain whether fresh tariffs will greet them at British docks. The March 29 Brexit deadline may be extended because of Westminster paralysis, but the odds remain that we Brits will exit regardless of the damage to our economy, culture and society. The possible cliff-edge catastrophe of leaving with no deal still looms.
Already there are signs of the impact as firms shift assets abroad, growth slows and investment plummets. Nissan's recent decision to ignore a $76 million state bribe to build a new car at its factory in Sunderland was significant. Sunderland is a northern city that voted heavily for Brexit, and Nissan's auto plant is a symbol of Britain's 1980s revival under then-Prime Minister Margaret Thatcher. She sold the Japanese firm on the idea of locating there by touting Britain as the "gateway to Europe," inside the world's biggest trading bloc yet freer of red tape than its neighbours.
Thatcher's revival of a moribund automobile industry by encouraging foreign ownership symbolised Britain's economic renaissance, along with the even more important 1986 deregulatory "Big Bang" opening the London financial district to investors from all over the world.
Brexit's economic impact is likely to unfold slowly, even imperceptibly, at times. But it will be just as significant as firms invest elsewhere, exacerbating problems in struggling areas that backed Brexit and reducing state revenue. James Dyson, a leading Brexiteer and tech billionaire, has already announced that he is shifting his headquarters to Singapore.
Britain sent out a message that it is replacing bridges with walls - walls less obvious but more of a barrier than the one Trump wants to build. Even if Ireland stays peaceful, Scotland does not break free and London retains its artists and bankers, the Brexit message will erode the wealth and strength of a country that was revitalised by globalization. Meanwhile, the mother of parliaments has gone mad, the governing Conservative Party shows contempt for business, and its Labour rival has been taken over by lovers of Karl Marx.
Trump is terrible. But Brexit is a bigger and more enduring act of sabotage.
Ian Birrell was a speechwriter for former Prime Minister David Cameron and is a contributing editor for The Mail on Sunday.
