Jeffrey Sachs is a professor and director of the Center for Sustainable Development at Columbia University. The opinions expressed in this commentary are his.

(CNN) Maybe Donald Trump really is the Manchurian Candidate, a stooge of some foreign potentate. Much more likely, Trump is just mentally unstable and narcissistic. Whichever it is, Trump is rapidly destroying American global leadership, alliances, and interests. Wednesday's announcement of new tariffs on steel and aluminum exports from Canada, Mexico, and the European Union is the latest bizarre and self-destructive move.

Jeffrey Sachs

I have just returned from a trip to Europe. Across Europe, there was not a single word of respect for Trump. The constant refrain was extreme puzzlement and deep consternation. How did America fall so far so fast? What do we need to do to survive?

Trump's so-called policies are not really policies. Trade wars are on, off, on hold, on again, within the span of days. Summits are on, canceled, or maybe on. Foreign companies are sanctioned today and rescued the next. He says o ne day he would like to see overseas troops called home soon, and tells them to stay the nex t. Global agreements and rules are ripped to shreds. Trump's garbled syntax and disorganized thoughts are impossible to follow.

The US has probably never before had a delusional President, one who speaks gibberish, insults those around him including his closest associates, and baffles the world. By instinct, we strive to make sense of Trump's nonsense, implicitly assuming some hidden strategy. There is none.

Trump's trade actions are blatantly illegal. They are flimsily justified as an act of national security, but this is sheer nonsense. They are also fatuous in terms of US economic and geopolitical interests. Harming our closest allies, raising the prices on key intermediate products, and provoking retaliation cannot possibly deliver higher wages, better jobs, or an improved trade balance. Trump's latest notion to slap tariffs on German automobiles would be even more damaging geopolitically.

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