For example, networks like BBC America fell under less scrutiny because legacy regulations around paid cable broadcasters were less stringent than those given to free airwaves.

Internet communications are functionally paid cable broadcasts.

That all being said, all of these regulations, old and new, are basically trying to do the same thing - limit propaganda opportunities for adversarial actors.

They are not, and that's where this line of argument falls apart. The purpose of these regulations is to limit ownership of media institutions not propaganda opportunities for adversarial actors. If Steven Mnuchin's group wants to take ownership of TikTok and run identical content, he's free to do so. The important thing is that his insider business partners lay claim to the profit generated by the property.

What's more, if Mnuchin is under the influence of a foreign government - his Saudi investors or UK/German financial allies or even other Chinese state actors using his firm as a foreign investment vehicle - that's also fine from the perspective of the US government.

While it is inevitable that a Mnuchin owned property will see editorial content in line with his Trumpy friends, in the same way that Elon's takeover of Twitter has turned it into a slurry of Apartheid South African style bigotry, this isn't the purpose of the forced divestment. It's just an anticipated consequence.

IMHO, it doesn’t seem unreasonable to look at what’s going on in Taiwan and Hong Kong, and say “maybe the CCP shouldn’t have easy access to a major media algorithm where stars are literally praised for their ability to ‘influence.’”

Wrt Hong Kong, isn't this exactly what they were protesting? Chinese bureaucrats stepping in and closing off communications to the outside world, on the grounds that American liberal media might trick Hong Kong residents into violent disruption of the municipal economy?

If you're a Free Hong Kong kind of guy, I would think the pacification of the city under Beijing rule is exactly what you don't want to see. Similarly, in Taiwan, if people are being cut off from communicating between the island and the mainland, I would say that's sending these two regions in exactly the wrong direction.

It's akin to the mistake the Great Powers made wrt North/South Korea or East/West German during the Berlin Wall era. These divided states ratchet up tension as individuals lose contact with one another and states become a hot-house of domestically produced misinformation.