Google isn't top of the list - because it's way easier for a user to stop using, than MC and Visa networks.
I would argue for an EU type approach and instead of regulating Google or payment networks - force demonopolization and opening up markets to more competition.
If you wish I can even share the priority list in my mind, for what sectors require addressing before Google:
1. Actual local monopolies
2. Local education sectors and their organisations
3. Radio spectrum for local wireless internet and cable providers (to challenge local cable monopolies)
4. Banking and payments systems
5. Construction sector
... basically there's 99 problems and Google ain't one.