Single device for digital to analog television signal conversion
Does a device exist that can do the conversion for all channels?


Not simultaneously, so far as I know. Typically a "set-top box" (digital decoder) can decode a single channel at a time. You can get two or three channel devices at higher cost but so far as I know there's nothing that simultaneously decodes dozens or hundreds of digital channels and multiplexes them into an analogue signal on a coaxial cable from which multiple analogue TVs could select an analogue channel.

So you have to use the remote for the set-top-box to choose a channel.


  and all the other TV's in the house could be controlled normally.


Not for choosing a channel


  so the channel could be changed on the TV and not with the box?


No.


  I ask this because devices such as VCR's, DVR's, and USB tuners would suffer from not being to change the channel through their own programming.


Annoying isn't it. Welcome to the future.