That's big, but in the minds of most, that's not a monopoly. Duopoly with Google, sure, but convincing a court of a monopoly when a lot of people in that court have living memory of Windows being 80%+ of the total OS installs in the country is going to be a tall ask, especially considering that didn't even stick, long-term, as a rationale to keep MS under the original terms of its punishment.

Windows (Microsoft) never tried to charge 30% on top of all commerce occuring on the platform.

What would your opinion be if they did?

IMO, it's the interop that that will potentially get Apple. The stuff about the store and fees will likely end up nowhere in the US.