Google ads are a natural monopoly, like power lines. What are you going to do, go to 1/3 of its ad customers and tell them they're switching to Southwestern Google while another 1/3 have to switch to Pacific Google?

This assumes Google search - the main reason they have a business - will remain popular. That’s a very big assumption.

Google’s monopoly isn’t “natural”. It’s temporary.

I was thinking of AdSense.

And then one of them becomes dominate after 5 years, and the other(s) fold. It's an inevitable problem. The only way to "break them apart" that would make any sense at all would be to break off distinct divisions, like Search, YouTube, Gmail, Google Cloud, etc. Into separate companies. Then forbidding them to acquire each other, and generally be extremely pessimistic/restrictive if any of them attempt to acquire any company at all.

Sounds like a good plan. I think the tech ecosystem would benefit greatly from more competition.