Then Trump went ahead and threatened major new tariffs on Mexico, not because it had violated its trade agreements, but because he didn’t like something that was happening on the border, a situation that has nothing to do with trade policy. So the USMCA appears, in practice, to be a solemn promise by the U.S. government not to impose tariffs on Mexican products … unless it feels like it.

If that’s what you get out of making a deal with America, why bother?

And then, after all the dire warnings of what would happen if Mexico didn’t give Trump what he wanted, Trump appears to have backed down in return for a declaration that Mexico will do pretty much exactly what it had already promised to do before the threats.

Now, the business world is extremely pleased that the trade war appears to have been called off. But it does look as if a Trump threat is worth about as much as a Trump promise: There’s no particular reason to believe that he’ll actually go through with it.

The only thing we can be sure of is that whatever happens, Trump will claim to have achieved a great victory.

In the case of the Mexican standoff, this may not seem too bad. But think about what it means when foreign leaders know that the president of the United States is:

(a) gullible

(b) easily susceptible to flattery and

(c) eager to proclaim victory, and unwilling to admit that he didn’t actually get anything significant.

Basically, this turns America into a systematic chump. Hold a summit, flatter Trump’s vanity, let him issue a communiqué claiming vast achievement, then go on doing whatever you wanted to do. Just ask North Korea’s Kim, who snookered Trump into thinking he’d made major concessions, went right back to building up his nuclear attack capacity, and still gets praised by Trump as our allies watch in horror.