Broadcast news and radio are limited to at most 20% foreign ownership by default [1]. Applying a similar requirement to large internet news distributors seems reasonable if they want to do business in the US (even if "banned" they could still distribute content, they'd just be restricted in making money).
"For example, they may start integrating technologies for which they have exclusive, or at least 'special' access. Can you imagine if all of a sudden Google apps start performing better than anyone else's?"
This is already happening. I very recently worked on the Edge team, and one of the reasons we decided to end EdgeHTML was because Google kept making changes to its sites that broke other browsers, and we couldn't keep up. For example, they recently added a hidden empty div over YouTube videos that causes our hardware acceleration fast-path to bail (should now be fixed in Win10 Oct update). Prior to that, our fairly state-of-the-art video acceleration put us well ahead of Chrome on video playback time on battery, but almost the instant they broke things on YouTube, they started advertising Chrome's dominance over Edge on video-watching battery life. What makes it so sad, is that their claimed dominance was not due to ingenious optimization work by Chrome, but due to a failure of YouTube. On the whole, they only made the web slower.
Now while I'm not sure I'm convinced that YouTube was changed intentionally to slow Edge, many of my co-workers are quite convinced - and they're the ones who looked into it personally. To add to this all, when we asked, YouTube turned down our request to remove the hidden empty div and did not elaborate further.
[1] https://www.foster.com/newsroom-publications-The-Road-Map-Fo...