Think of it as a situation where taxes effectively force people to take some action because the action is cheaper then paying the tax. People who want to take that action anyway may go well beyond the minimum needed to avoid the tax, but everybody is going to do that minimum amount.

Other countries have to buy a certain amount of US debt* or suffer greatly in trade.**

Countries like China that want to encourage trade with the US can gain further advantage by pushing their currency down further.

Jay

* Theoretically they can buy anything the US exports. But we import far more then we export, meaning they have to buy US debt or buy US properties (buildings, companies, land, that sort of thing). And the second is much more complicated.

** And it's not just trade with the US. In an ideal economic model, where countries trade in their native currencies, countries can shift exports and imports around to avoid such imbalances. But the US domination of global finance is such that most international trade is denominated in dollars, no matter what countries are involved.