The US doesn't need to produce yachts (or this particular type of yacht), thats the whole idea of trade, you specialise in some things not others, and everyone ends up better off. There are a huge number of components in a yacht, many American. And financing and so on.
That's not relevant to the point (although I'd also disagree with this entire premise, the root of tariff-free global trade). The point is that when someone (e.g. Bezos) spends US$500M of realized gain, it doesn't necessarily get spent in the USA. That's all.
