For the US to start taxing Apple's foreign income abroad is not like taxing an American living in Ireland (and even that is crazy). It's like if the US started taxing an Irish person in Ireland[1].

However obvious it is that EU Apple is a sock puppet of US Apple, directly imposing taxes on foreign companies operating in foreign countries would be met with retaliation. It is not a smart nor a profitable trade policy.

[1] This actually does happen: https://en.wikipedia.org/wiki/Accidental_American