I think ultimately the director wants “the world to save the world”. In the first movie, more than one of the engine was fired up to blow up Jupiter, instead of solo heroism that one team saves the day. In the second movie, astronauts from all nations volunteered as a symbol of courage for mankind. Granted the story was told from China’s perspective but I think it just happens to be they chose China’s wandering earth plan instead of other countries’ proposal.

If I am a Brazilian fan, I can still write a fan work on how Brazilian astronauts contributed and saves the day within the same universe.