The USA supposedly have the most data in the world. Companies cannot (in theory) train on integrated sets of information. USA and China to some extent, can train on large amounts of information that is not public. USA in particular has been known for keeping a vast repository of metadata (data about data) about all sorts of things. This data is very refined and organized (PRISM, etc).
This allows training for purposes that might not be obvious when observing the open weights or the source of the inference engine.
It is a double-edged sword though. If anyone is able to identify such non-obvious training inserts and extract information about them or prove they were maliciously placed, it could backfire tremendously.
Transoceanic fiber runs become a very interesting resource, then.
And I think we can already see this. The gains in LLMs are increasingly marginal. There was a hugeeeeeeee jump going from glorified markov chains to something able to consistently produce viable output, but since then each generation of updates has been less and less recognizable to the point that if somebody had to use an LLM for an hour and guess its 'recency'/version, I suspect the results would be scarcely better than random. That's not to say that newer systems are not improving - they obviously are, but it's harder and harder to recognize those changes without having its immediate predecessor to compare against.
It's also doomed to failure because of how transparent this is, and how abused previous dependencies (like the USD) have been. Every major country will likely slowly move to restrict other major powers' AI systems while implicitly mandating their own.
And about your thought: I disagree. When I look at those online places, I see echo chambers, trolls and a lack of critical thinking (on how to properly discuss a topic). Some parts might be artificially accelerated, but I don't see propaganda couldn't be fought. People are just coasting, lazy, group thinking, being entertained and angry.
Propaganda is less about what it says, but more about how it makes people _feel_.
If you get the feels strong enough, it doesn't matter what you say. The game is over before you start.