Historically, anti-trust authorities have been more concerned about horizontal integration, not vertical integration. On top of that, Apple is not even the largest phone maker in the US, owning around 13% market share. For an anti-trust suite to be successful, the prosecutor needs to prove consumer harm, and that will be hard in this case. (IANAL.)
There are actually two changes that would need to be made for my post to work.
First, that the law should acknowledge that Apple has 100% market share on every patented feature, and therefore they have a monopoly, not on smart phones, but on "smart phones with rounded corners" and numerous other design decisions and features that they have chosen to patent and gain a monopoly on. This is a change in how the relevant market is defined.
Second, that any prevention of competition in after markets should be illegal, not just prevention of competition in after markets that consumers weren't aware of when they bought the device.
Consumer harm here is trivial. That want to use an app, they cannot, that is harm.
(Ianal either, but spent a lot of time reading about this sort of issue)
