Hmm, I have a Fire TV box that will turn my flat screen on/off, among other functions. Don’t know if Amazon has an available SDK for Alexa type devices.
There are all sorts of devices and software to control outlets. The problem there is cutting the power to your TV, when really want you want is to put it in standby.
Maybe something with a Logitech Harmony interface?
Here’s a thread to start from -
I don’t think that you’re going to find anything off the shelf, but maybe some of the more adept tinkers will cook something up.
It’s an interesting idea, tho.