Foreign countries knew Trump was not mincing words. When he made a threat, they knew he could and would back it up. Today, they just laugh at Biden and the US. Hard to believe we've gone from a self-sustaining super power to a wimpy no-teeth nation looking at a recession in just a couple of years.
Trump was used to an environment where two antagonists would negotiate and find some common ground in the middle where both could walk away satisfied with the outcome.
I don't know if it's in "The Art of the Deal" but at least once he said that you BEGIN negotiations with the most lopsided, extreme position you can even hope to get. Your first offer is the worst one - it's where you offer to give nothing and get it all. You come back and each time, you give a little more ground and come closer to agreement - until you arrive at an agreement you were willing to go with from the very start.
THAT is how you make a deal.
But in POLITICS, especially American politics, that's all bass-ackwards. Politicians START with the sweetest deal they can offer, hoping you'll snatch it up right away. In negotiation with foreign entities - that's ridiculous, because THEY all know how the game is played. When you haggle on the street with a vendor, you don't BEGIN with the asking price - heck, you START with a price so absurd, they're ready to walk away.
The problem in politics, especially LATELY, is that politicians are eager to walk away WITH SOMETHING, however bad it is. If you've ever haggled over a car, the worst thing you can do is let the salesperson know you don't plan to walk away. THEY want the sale - heck, if you threaten to walk away and they believe it, they'll try to tell you you won't get a better one elsewhere - the others will be the same ("Fine with me - THEY will get my money, but not YOU").
With Trump, it didn't have to be the end of the world, but he was completely willing to walk away from a deal, because it's how he negotiated his entire life. The *******s in Washington just weren't used to the idea.