About two weeks ago I wrote a commentary, “Unfit to Command,” which argues that Donald Trump lacks the temperament, intelligence and leadership qualities to be in charge of U.S. foreign policy. He makes a habit of shooting from the lip (i.e., tweeting), lying and making policy proclamations without consultation.

He also seems incapable of acting calmly, deliberately, and sensitively, preferring instead to veer suddenly in a particular direction rather than consider the repercussions.

Last but not least, Trump seems oblivious to the prospect of negotiating differences with friend and foe alike.

I write this as news appears of Mexican president Enrique Peña Nieto’s cancellation of his visit to Washington.

He made the right decision; no self-respecting head of state should have to endure insults from a US leader — and let’s face it, building a wall between Mexico and the U.S. to keep out “rapists” and drug dealers is insulting, and punishing Mexico for refusing to pay via a 20-percent tax on imports from Mexico is doubly insulting. Of course Trump tried to trump the cancellation, contending (in a tweet) that Peña Nieto should not come if he didn’t intend to pay for the wall. No dialogue, no softening; just adding insult to injury.

So thus far we have two major trade agreements — the North American Free Trade Agreement (NAFTA) and the Trans-Pacific Partnership (TPP) — that Trump is ending. I’m as critical of these agreements as the next person, but Trump’s way of handling them has less to do with their terms, which can and should be renegotiated, than with his king-like way of disposing of problems.

But they can’t be disposed of: Trump’s approach irreparably harms U.S. relations with its neighbor, just as it seriously undermines relations with Japan and other Asian countries that wanted the TPP as an offset to China’s economic dominance.

Consider the viewpoint of prominent Mexicans, as reported in the Washington Post:

“When we are talking about building a wall, about deporting migrants, about eliminating sanctuary cities [for migrants], about threatening to end a free-trade agreement, or to take away factories, we are really talking about causing human suffering,” Margarita Zavala, a possible candidate for the presidency in 2018 and the wife of former president Felipe Calderón, said in an interview. “And after today, without a doubt, it is very difficult to negotiate from behind a wall.”

Mexicans had trouble recalling a time when relations were this bad with the United States or when an American president appeared to be such a threat to Mexico’s core interests.

“Never,” former president Vicente Fox said in an interview, when asked if Mexico had faced a comparable U.S. president in his lifetime. “And I never thought the U.S. people would go for a president like this.”

“We don’t want the ugly American, which Trump represents: that imperial gringo that used to invade our country, that used to send the Marines, that used to put and take away presidents most everywhere in the world,” Fox added. “That happened in the 20th century, and this is what this guy is menacing us with.”

As we have come to learn, Trumpian arrogance applies virtually across the globe, Russia being the great exception. His “America First” doctrine has alarmed the Europeans — other than the groveling British prime minster and other anti-immigrant nationalists — and raised concerns about the viability of the European Union and the North Atlantic Treaty Organization.

In Asia, Trump has rattled the Chinese over his indifference to the “One China” principle and apparent readiness for a military confrontation in the South China Sea. U.S. friends in the region are already leaning toward China in economic affairs; the Philippines is not alone. Meanwhile, all those individuals and organizations abroad that look for U.S. support as they promote respect for human rights, environmental protection, health care, and social justice are getting the message from Washington that America First doesn’t embrace their concerns. Defeating Islamic terrorism is the main U.S. mission abroad, and “civilization’s,” said Trump in his inaugural address.

In response to the Trump administration’s radical change of direction on so many fronts, we’re already seeing major defections in the State Department and rogue tweeting activities in the Environmental Protection Agency, the National Parks Service, and the National Aeronautical and Space Administration. I expect many more resignations to follow, particularly from within the intelligence community that Trump so clearly disrespects. The case for impeachment grows, for as I’ve written before, Donald Trump is a threat to national security.

Mel Gurtov, syndicated by PeaceVoice, is professor emeritus of political science at Portland State University and blogs at In the Human Interest.