I’m not sure the people of Hong Kong, Taiwan, or Tibet would necessarily agree with that portrayal of China.

If you’re not sure, then look into the history of those three regions of China before you make any hypocritical remarks, especially as someone from a genocidal settler colony like Canada

Why? Let’s say this was still the example… Couldn’t the reach of the Vatican and its billions of followers make a meaningful impact?

It’s far from billions, but sure, hypothetically, if all followers of the Roman Catholic Church somehow managed to seize state power in their respective countries and started producing renewable energy, it would be meaningful. Back in reality, that’s nothing but a thought experiment, and in case you genuinely didn’t realize, my use of Vatican City as an example was because of its size