Walter you make some huge assumptions.
First, how many ISP's are there in North America? What makes you think ISP's are going to invest in the infrastructure to make this happen? What incentive do they have? That still some mighty big pipes required!
The whole point behind multicast is that it does NOT
require N times as much gigabytes (or bandwidth) to reach N times as many customers. A really simple proof of concept is to take the case of an old Netgear ADSL router I had a few years ago, before command-line became passe. You could tell it to send logging info (internet scans/attacks/whatever) to a computer for logging. I chose to set the destination to 192.168.1.255 which also happened to be the "broadcast address" for my small "LAN" (2 computers). The result was that both computers could pick up the logs, even though the traffic was identical to sending the logs to one computer. This obviously works only with connectionless UDP for a one-way broadcast. But that's what TV is, anyways.
There is also "promiscuous mode"; see http://en.wikipedia.org/wiki/Promiscuous_mode
Ethernet on a LAN/WAN already has everybody's traffic on it simultaneously. The default is that the OS tells the network card to ignore any data not addressed to it. The OS can tell the card to listen to one other signal. The main problem is that the OS will bog down when trying to process multiple data streams.
Most North Americans don't have an internet connection that can handle 19.4 Mbps (perhaps 10 Mbps if compressed) for one channel.
That's ATSC. QAM is 1/2 of that, i.e 9.6 Mbps for the identical quality. Many cable systems put 3 HDTV channels into 1 QAM channel without noticable degradation, so we're talking 6.4 Mbps. That is difficult today, but attainable.
What if you have 3 televisions in your home?
OK, you're out of luck if you want to watch different channels.
Maybe not but you need some type of converter box that connects to the internet to convert those MPEG-4 streams to something your television can use. Whose going to pay for that?
The same people who currently pay $250 for a Rogers HDTV terminal. See https://www.rogersdigitalcentre.com/add/orderform
I'm sure it doesn't really cost anywhere near that much, especially if it doesn't have auto-update and remote control from Rogers, and PPV handshaking, and DRM decryption, etc, etc. You don't need most of those "features" in a simple box that outputs HDMI or component video. If all else fails, use your PC.