What's the difference compared to a phone with a radio firmware by a US company?

In both cases it's something closed and the government has shown overreach. (Yes, China a lot more than the US, but still ... things are not looking good a the moment. And I have no more trust, even if the political direction changes for a presidency period or two.)

But yes, ultimately we want open source firmware. Still, then there could be hardware backdoors anyways ...