The phrase “national emergency” conjures up images of riots in the streets and burning cities, a disease pandemic killing millions, or an inter-planetary invasion by little green men from Mars.

Donald Trump’s national emergency, over his thwarted plans to build a border wall with Mexico, is prompted by none of these horrors. According to him, the safety and wellbeing of the world’s richest, most powerful country is threatened with utter destruction by penniless Guatemalans.

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“It’s an invasion. We have an invasion of drugs and criminals coming into our country,” Trump claimed on Friday. “We’re going to confront the national security crisis on our southern border and we’re going to do it one way or the other.”

With these words, Trump served notice on Central American asylum seekers fleeing crime and poverty that the Land of the Free is closed – to them at least. The Statue of Liberty is looking the other way.

One has to admire Trump. Any other president, when facing so dire a menace, would be hunkered down in the White House situation room, masterminding the fight for national survival. Not him. No sooner had he made his dramatic declaration than he set off for a golf weekend in Florida.

What wondrous sangfroid; what exemplary courage under fire. Or could it be the “national emergency” is not an emergency at all?

Official figures give the lie to Trump’s Rose Garden amateur theatrics. Illegal border crossings are at an historical low, down from 200,000-plus in 2001 to about 40,000 last year. Likewise, the number of people apprehended or turned away has decreased significantly over the past decade.

The main rise this year has been in unaccompanied children and families. Trump’s “invasion” is an invasion of kids.

It is true the US has a serious drug problem. But that is principally a problem of demand, not supply. The current opioid epidemic is but the latest manifestation of a society long prone to chronic abuse.

The first US opium commissioner, appointed by Theodore Roosevelt, described Americans as “the greatest drug fiends in the world”. Border drug smuggling is the symptom, not the cause. Ironically, funds Trump now plans to seize to finance his wall come from counter-narcotics budgets.

Trump’s faux emergency, like the self-defeating government shutdown that preceded it, reflect the Alice in Wonderland nature of American politics under this president. On some interpretations, Lewis Carroll’s famous story is an extended metaphor for drug use.

Like the Cheshire Cat, Trump grins enigmatically as one bizarre and weird event follows another. Like Alice, wincing Senate Republicans drink potions and figuratively chomp on magic mushrooms to escape the too-real travesty this White House has become.

How else to explain such surreal happenings? On one reading, by insisting on building the wall by decree, Trump is simply securing his nationalist America First voter base.

On another reading, he was petulantly reacting to claims from popular conservative pundits such as Sean Hannity and Rush Limbaugh that he had taken a beating from the Democrats. Ann Coulter, a venomous rightwinger, remains unappeased. “The only national emergency is that our president is an idiot,” she snarled.

Trump’s emergency is historically, constitutionally and legally contentious. It is already being challenged in the courts, and the resulting delays could be indefinite. Yet this is surely no surprise. This move mirrors other, familiar aspects of his leadership style.

The declaration, or attempted diktat, is the arbitrary action of an instinctive autocrat. It trashes convention, and co-equal Congressional rights and oversight. It is the product of an immature, egotistic mind. And it is based on a lie – namely, that Trump repeatedly promised he would make Mexico pay for the wall, not US taxpayers.

More than anything, the wall is physically as well as politically divisive – and division is a trademark of Trumpism. It features in almost everything he does, whether the issue is race in the US, gun control, press freedom, Venezuela, Iran or the Israel-Palestine conflict.

Trump is not alone in his myopic, fearful outlook. Walls, or the more euphemistic, antiseptic “separation barriers”, have been proliferating globally in recent years – in the West Bank, between India and Pakistan, and between EU countries, the Balkans and the Middle East. Another may soon be erected, in one form or another, on the island of Ireland.

The world can be divided into those who build walls and those who build bridges. There is no doubt which side Trump is on.