If I go to a restaurant, wait an hour for a table, get very hungry, and then see on the menu that the restaurant has tripled prices, is the restaurant "negotiating from a position of power" ? Sure, once.
What exactly do you think happens to our power after Trump squanders it to extract one-time concessions that mostly flow into his own pockets?
The last vestiges of this world order was the TPP. The US negotiated a trade deal that would cement its top position in the Pacific region, while curbing China's growing economy and influence.
And then Trump axed it, because he didn't understand it.
China understood perfectly what an opportunity that was for them, and they have been quietly become less and less reliant on trade with the US since.
The current US regime is now hell-bent on dismantling the remaining alliances, relationships, and trade agreements that actually kept the US on top, the ones that actually kept the US powerful.
...while baselessly claiming that the existing world order was somehow "unfair" or "a bad deal", and that whatever the hell they're doing now is restoring some kind of lost power. They clearly have no clue what the source of America's power really is.
And here you are repeating their talking points.
What do you mean, exactly, when you're saying that the US shouldn't "let the world do whatever they want" ? What specific trade policies do you think are unfavourable to the US?