Facebook, Google, Apple, Amazon -- the US could easily break all of these up. There's a huge risk to stagnation and over-optimization once these companies get as big as they do.
Facebook: Instagram, WhatsApp, Oculus
Google: DoubleClick, YouTube, Android, Waze, Deep mind
Amazon: Whole Foods, Audible, Zappos, Ring, One Medical
Arguably, I think things would be better if a bunch of these acquisitions were never allowed in the first place. But most of Apple's acquisitions have been of the "acquihire" type where they got specific technologies to enhance their products - Beats is the only one I can think of off the top of my head that has basically remained separate.
I'm not saying acquisitions are the only benchmark for breaking up big tech, but to me it feels like the places where Apple is anti-competitive (e.g. App Store) can be remedied with much smaller changes than a full break up. With the other 3 it seems easier to identify places to "cleave".
If they had to separate their operating systems into another company, they would have to freely compete to put their app stores on their devices.
Or even better, spin off their hardware divisions if you want.
Either way Apple shouldn't be able to control their operating systems or their hardware unless they open up their devices and allow consumers easier ways to both repair their devices and install alternative operating systems on them.
I think it's a much harder argument to make that Apple should get to control all application software used on a device, and furthermore that they have a right to a cut of all revenue of app software sold for a particular device.
It's why I added they should be legally compelled by a consent decree to provide parts, schematics, and the ability to change operating systems seamlessly if they want to keep their monopoly.