The EU app store--even as a separate legal entity--doesn't operate independently: it takes its marching orders from Apple, Inc., and Apple, Inc. has been required to not do this thing to developers, not merely directly but indirectly even by persons (which includes corporations) they are merely "in active concert or participation with". The EU app store doesn't even have a separate submission portal or a separate approval process, much less any autonomy in its operation: it is certainly covered by this injunction.
Tax law do not work according to International Law. It works according to State Law. US Law treats revenue as either local or foreign. Local revenue gets local tax. Foreign revenue gets foreign tax. When the profit from foreign revenue makes its way to the US parent company, it is seen as local revenue.
