Yes it relies on Google keeping their key (or keys - there's nothing wrong with having multiple valid certificates for a domain, especially if you're the registrar) private. Google keep their key private, Amazon keep their key, Stripe keep their key. If you want to attack any provider you have to recover that provider's key.

Now if you mandate everyone use a government key or escrow their key with the government there's now a single place to attack. Also this place is affected by government whims, staff pay freezes, cutbacks, layoffs. All you need is one disgruntled employee or contractor with access and you now have access to _everything_.