Hmmm, I’m good at picking up details and patterns and making a mental map of them, but not so much at elaborating and explaining them in depth. It has been explained much better by larinah on this post, that I have yet to finish reading, but that makes some very interesting observations about TVs, and neven-ebrez here, here and here (I suggest “ctrl+f”ing the word “TV” to find the exact paragraph, because it’s quite a long post), but I’m quite excited that you actually came to my inbox to ask about it, so I’ll do my best to explain the way I see it.
First of all, I started noticing Cas’ connection to TVs on season 8. Prior to that, I remember having some vague notion that Cas liked watching TV while working with the Winchesters because of his porn watching on Caged Heat, but I hadn’t really thought about it. Then, in A Little Slice Of Kevin, after Cas came back from purgatory and got cleaned up, we see him zapping through some channels, stopping on one that shows a space view of the earth, and smiling to the TV, not looking at Sam at first while talking to him, before he turns it off and walks over to them. In the next episode, Hunterii Heroici, TV has a more important role, it is fundamental to understand the case, and Cas watches it as part of their research.
That scene in 8x07 seemed really sweet to me when I watched it because it almost looked like the human way of watching over the Earth, like Cas had done for milenia before rebelling, but in a way that allowed him to actually be close to his chosen family and to the humans he watches over. Notice how he turns off his “watch” to walk over to Sam and Dean, like he has done so many times before. And then in Hunterii Heroici it is also a means to learnig more about humanity, when he watches the cartoons and comes to the conclusion that it’s hilarious because of the way it symbolises humanity’s search for the divine and inability to really grasp it. That is, he is drawing meaning and learning lessons from his humanity watch, and the message he gets from it can be related to his own story in eight thousand different ways. Not only that, but the psychic used it as an escape from his responsibility and his life in general, thus unintentionally hurting those around him, and at the end of the episode, after having entered the mind of the psychic and having heard his speech, he gets to the conclusion that he should stop running away from his responsibility in Heaven and finaly face up to what he did (even if there was some meddling from Naomi on that). (Also, I just realised how little I actually remember from that episode, so that last thing I wrote may not be entirely accurate)
After that, you have Goodbye Stranger (“Would it kill you to watch a movie? Read a book?”), and Clip Show, when they are watching that video of the demon cure and in a piece of hilarious foreshadowing Cas is the only one eating popcorn, but I’m not gonna really say much about that because there are not TVs involved per se.
Then, in Sacrifice, there’s the cupid bar scene, with the arrows on the TV pointing first at Dean and Cas and then at the other future couple, but this has been talked about a million times before so I’m not going too deep into that one either.
At the beginning of season 9, when Cas is human, we see him a few times watching the news about the angel fall on the TV. The human way of watching over humanity is the only one he has left at this point, and it shows him his own story, for he is now human himself, even if the ones shown on TV are the angels now.
And then comes Holy Terror, and I’m gonna copy-paste what neven-ebrez said on her review:
Cas walks over to the TV. He turns several knobs, but the television will not turn on. The TV is not working. It does not have any power. Its purpose: providing entertainment and comfort can not be acheived without power going into it. And… there’s your second piece of foreshadowing this episode for Cas getting his grace back. A muffled voice comes from outside the room. "Try plugging it in."
Cas grabs the angel blade on the torture tray and slashes Theo’s throat, exposing his grace. Cas siphons it out, plugging the proverbial TV back in and repowering his angelic construct. Cas is instantly healed as Theo stands speechless. Cas reaches out his hand and gives the tv a proverbial “channel flip”. He gets the smiting channel. Cas does not look happy about what he’s about to have to do as he looks towards his escape route. There is more symbolic whistling, (this time from Malachi), as Cas, like Dean, heads “back to start”, having wiped out all of Malachi’s henchmen by taking back his false shield of identity.
All the other times we saw Cas with TVs, human means were enough to turn them on and off, but this time they’re not, so he sees himself forced to resort to angelic means. His recovering his angel power stems from an inability to affect events the way he wants them to solely with human means, so his angelic powers are a route he feels forced to take.
And right on the next episode, we get to the deleted scene with Cas and Crowley. As zerbe said on the second of her posts I linked, they are watching “the death of humanity”, the TV is still telling Cas’ story. Right as he gets angeled up again, he suddenly stops using human means to turn off the TV, because those are in the hands of other evil manipulators, so he has no choice but to use his angelic means again. And what happens this time? He doesn’t just turn off the TV, he breaks it, because there’s something really wrong about his new powers, they’re not working the way they are supposed to be, and maybe they’ll end up breaking Cas too.
Another observation, something I noticed while writing this, is that the only time we see a modern, flat-screened TV is in Heaven Can’t Wait. All the other times, times on which he was an angel, or about to be again, the TVs were old as fuck. I know I’m not the only one who has thought about this because I’ve seen other people talking about it, even if I can’t remember who they are right now, but there have also been lots of contrasting new things/old things combos, mostly to symbolise Cas’ strugle between his new and old identities. The clearest example I can think of right now is in the Sneak Peek for season ten, when he’s laying in bed, and there are a new phone and an old phone by his bedside, and it’s the new one he takes to answer a call from his new family. Apparently also happens with TVs.
And well, this turned out a lot longer and better than I was expecting, so thanks for bringing the question to me and helping me put my thoughts in order, nonnie ^^