When it comes to his country’s relationship with Mexico, US president Donald Trump has decided to take a position that is at once reckless and suicidal. Reckless, because he is single-handedly scuttling a bilateral relationship with a nation that is vital to the prosperity, security and wellbeing of the US. Suicidal, because the punitive tariffs he threatened on all Mexican imports a little over two weeks ago would only boomerang and smack America in the face.

The lessons from what is surely the gravest diplomatic crisis between the nations since the murder of an undercover US Drug Enforcement Administration agent on Mexican soil in 1985 are worrisome. First, there’s the resounding message to the world that the US cannot be trusted in any negotiation (despite having just finalised the revamp of a new regional trade agreement). Second, they are a reminder of what happens when Mr Trump is allowed to continue weaponising trade policy. Third, they underscore that he will continue to conduct foreign affairs by means of tirades, ultimatums and tantrums.

The US president will never grasp why tariffs on Mexican exports are a self-inflicted wound. The integrated supply chains and joint production platforms that have been built in North America over more than 20 years of regional trade mean that out of every dollar that Mexico exports to the US, 40 cents are American inputs.