> It seems pretty speculative to me that there's some large database with all of the mandated software backdoors and keys to get access to.

You overestimate the competence of government agencies.

> Given everything else, I don't know how large an issue this is

A significantly large issue, seeing as it puts the safety of the vast majority of Americans at risk by exposing their personal information (everything from banking information to patient records to their precise movements).

> It would be interesting to see whether this is considered a threat scenario by the USG.

If it's not, then I've lost any sliver of confidence in the Feds that I might have had previously.