Not true, less than half of Apple’s revenue is from US, %42 last year. Europe is %26, China %16.

Apple would still be a viable business if it made 42% of what it currently makes.

Apple is amazing company and has amazing abilities, it's just that it doesn't have its own production ability and its %60 dependent on non-US consumer base. It will have to start producing its own products at %60 reduced market in the case of the hypothetical collapse of the global trade and supply chains.

So, even if Apple can eventually be fine is it going to be $4T fine?

Yes! But the point here is that producing apple products in the US would probably turn that 1000 dollar toy into 3000 dollar toy, which would in turn result in the sales going down as well.

Global economy means global price competition.

Another interesting effect is that industrial countries typically have MUCH lower average salaries.