Sometimes it can even be hard to know where a company has its "headquarters" as company can have shareholders from all over the world and various subsidiaries may have different shareholder makeups.

What do you think that means, if the headquarters location is irrelevant?

And what do you think does he mean with "Yeah, country of origin tariffs are 100% based on where it's made."?

He's saying. Tariffs are based on country of origin. They aren't based on company ownership because thats basically impossible to figure out with different shareholders.

In a weird way.

The EU can enact tariffs in any configuration it so chooses.

Nope, the EU is a WTO member and is therefor limited in the way it creates its tariffs. The only reason the EU is legally able to target US tshirts is because the US targets EU steel.

In this case, it would make little sense to tariff imports from China when the intent is to retaliate against the US. Why would they do that?

That's what I'm saying.

The EU cannot target products made by US companies in China. The EU cannot put a tariff on iPhones because iPhones are not made in the US. The EU cannot put tariffs on tshirts that are made on behalf of the US in Bangladesh. The EU can only target goods that are made in the US. Not made by a US company. Made in the US.