As long as you’re not disadvantaged compared to a Spanish seller of goods or services or Spain’s law is specifically violating an EU one, I don’t think so.
> for example geo-blocking within the EU is also illegal. if you offer a service or product in any EU country, then anyone in the EU must be allowed to buy it.
Definitely not. You’re not automatically obliged to sell to other EU countries just because you’re selling in one. There are some categories where you have to, but that explicitly excludes video streaming.
There is another regulation for subscribers temporarily traveling to a different EU country not losing access to a service they subscribed to in their home country, but that’s also something else.
according to my understanding yes, you are:
https://digital-strategy.ec.europa.eu/en/policies/geoblockin...
i don't see mention of any exception for streaming there either. (maybe one exists, if you have a reference, i'd love to take a look)
> [...] services in sectors currently fully excluded such as transport and audio-visual
if you look at the actual report summary however it shows that they want to change that:
https://digital-strategy.ec.europa.eu/en/news/commission-pub...
so even if not a reality in all sectors, removing geoblocking is in the interest of the EU.
going back to the original question:
Why should other EU members care what websites Spain allows their citizens to access? Does the "EU" even have authority for such a thing?
they do care, and they should, and yes, they have the authority.
personally, when i read the report, seeing how young people are more interested in viewing content from other countries, what first came to my mind is the increased integration of EU countries and cultures that comes from that. that's the why.