Trade wars, according to Trump, are "good and easy to win"; but he is about to find out that they are dangerous, messy and destructive.
They are destructive not just in economic terms but in geo-political terms as well. For the West's leaders, they signal the end of the close alliance that has exerted great influence in world affairs - and that significant turning point has been given added impetus by Trump's decisions to abandon his traditional friends by withdrawing from the Iranian nuclear deal and from the Paris climate change agreement.
The demise of "the West" was emphasised by the recent G7 summit, when Trump refused to sign the closing communique and found himself in disagreement with virtually all of his allies when he urged the re-admission of Russia.
His attack on the Canadian Prime Minister was simply further evidence of his lack of concern for the damage he had caused. He is likely to sow further dissension during his attendance at this week's Nato meeting.
The irony of all this is that the vacuum that has been created by America's withdrawal will be quickly filled by the other potential global superpower, China.
The increase in China's influence - welcome or otherwise - is already clearly apparent, not least in the Asia-Pacific region.
The recent Australian legislation, beefing up security against foreign influence was clearly directed at Chinese interference in Australian domestic affairs.
But it is not just in the international sphere that America has abandoned its long-held leadership role.
An important element in the Western hegemony that has dominated the world scene for so long has been the sense that the West represents the best way of doing things - that elements such as democracy, the rule of law, human rights and civil liberties, a free press, are all essential aspects of a successful society.
Yet it is precisely on these aspects of American society that Trump has launched his most bitter assaults, with the result that the US is no longer seen or held up as an exemplar of all that is best in Western values - quite the reverse.
Trump has succeeded in demonstrating that America democracy is deeply flawed - not least because it has shown itself capable of producing a leader like him - and can no longer be seen as shining a beacon light for the rest of the world.
Trump's surrender of any claim to American moral leadership is, of course, entirely consistent with his personal moral stance - his lies and his attitudes to women are all of a piece with his policy of separating children from their parents and holding them in cages.
It is hard to believe that the American people can stand idly by and allow such damage to be done to their history and values.
If American democracy is to mean anything, it must rapidly re-discover itself.
