Not trying to be argumentative or pedantic, but:

1. There are eleven states (California, Delaware, Florida, Illinois, Maryland, Massachusetts, Montana, Nevada, New Hampshire, Pennsylvania and Washington), covering around 1/3rd of the US population with all-party-consent wiretap laws.
2. States have slightly different wording, but like hidden camera statutes, it typically applies to electronically recorded communications and not just telecommunications.
3. That isn't really correct. I assume you're talking about the exception where there is no expectation of privacy. There are separate hidden camera laws that require disclosure at times even in public places, and even for wiretap some statutes are written in such a way that even public places with semi-private areas (e.g., a separated dinner table at a restaurant where your conversation may not be heard by others) may still support an expectation of privacy.

In all, since wiretap statutes are criminal statutes and Meta executives in theory could be charged if Meta is not only enabling but also directly receiving recordings from users, it's a pretty crazy risk they're taking.