It’s worth noting that there are other TLDs unrelated to Google that Route 53 doesn’t support (a prominent example is ai, which is nominally Anguilla but is of course used for something else). This is the nature of the (intended to be) competitive registrar business. Given my experience, …
… my own advice would be to treat your domain name registrations as something quite separate from your operating environment, and register everything with an independent registrar away from AWS. This is because of mistakes people make in integrated authoritative/registration interfaces.