They're intelligent social animals. Even just a change in eye contact from me alters my Amazon's behavior. He's incredibly attuned to my posture, tone of voice, mannerisms, etc, to clue in whether he's going to e.g. be getting a treat or scolded for misbehavior or whatnot. I can't imagine that a video without that back-and-forth would stimulate him.
I don't watch TV anymore, but he used to just tune it out. Rather, he'd tune into *me*. He'd laugh at the funny parts of shows and the like, not because he understood the humour, but because he was paying attention to me, and I was laughing, so he wanted to join in. And then I'd react amusedly to his taking part, he'd get attention, and getting attention was in turn a reward to him. They like getting reactions to the things they do. A video won't do that.
And yeah, he understands what screens are - same as mirrors. Some smaller psittacines are known to strongly interact with mirrors as if they're other birds, but in my experience, the larger ones don't do that; they quickly learn it's their reflection and stop caring. As a side note, I actually tried the mirror test with my Amazon twice, but each time I got a null result. You're supposed to put an unusual mark or lightweight object on their head where they can't see it, put them in front of a mirror, and if they interact with the mirror like it's another animal, they don't recognize it's their reflection; while if they use it to try to preen the hidden mark/object, it's a sign of recognition. But my Amazon didn't give a rat's arse. I might as well have put him in front of a wall for all it mattered; he gave the mark zero attention. Didn't care about the reflection of a bird. Didn't care about the mark on his head. Just sat there waiting for me to put him back on his cage :P I couldn't get him to interact with the reflection at all. Nor does he react to birds on TV. By contrast, he'll VERY MUCH interact with a real bird (he hates them all... he's very antisocial with nonhumans).