[djhn]

Implementation depends on the country and the broadcasters. I know nothing about US and Canadian broadcasting standards.

In Europe TV is in most countries sent over DVB-T2 (DVB-C2 in urban areas) which supports SD, HD and FullHD. The older standards, DVB-T and DVB-C, are still used in some countries and not everyone even plans to transition to DVB-T2. There are countries and broadcasters sticking with SD and 720p HD.[1]

The resolution of video content (SD, 720p or 1080p) is only approximately correlated with quality (there are numerous resources online comparing different resolutions at different bit rates and bit depths). I'm not a big broadcast TV user, but from eyeing various EU countries' TV broadcasts at hotels and the occasional sports bar while traveling, for the majority of your every day programming the quality corresponds to YouTube's 720p format (~2 MB/s), even if for example German TV is nominally 1080p50 H.265.

As an example, in most of the EU the 2024 Olympics were broadcast in 1080p. There was no 4K option available to purchase in many countries. The 1080p broadcast, however, had a very low bitrate, making it effectively equivalent to YouTube 480p/360p/240p. Many sports involving fast moving landscapes and water looked worse than in the 80s and 90s. Footage of water, in particular, compresses very poorly at constant bitrates because of the constant subtle motion of waves and reflections on its surface.

[1] https://en.wikipedia.org/wiki/DVB-T2