This case is about the US marketplace, globally is irrelevant.
And it is about more than just marketshare. Apple's tactics restrict the entire marketplace --- not just Apple captives.
Whole classes of apps are simply not practically possible on Android without paying monetary tribute to Apple.
For example, universal messaging is not possible without paying the Apple gatekeeper. Few people will use a messaging app if it can't communicate with 60% of their friends. And the only to make this happen is to pay Apple.