I'm pretty sure when China banned Google & Facebook, it cited the reason as "not obeying local law" and "posing a national security threat".

It was less national security and more not obeying local law, particularly the law mandating censorship of certain stuff.

I don't like the Chinese approach to managing the public opinion by censoring valid information and opinions at all. But the opaque and uncontrollable pockets of power created by the US approach of misusing "national security" as an excuse for practically any action, most of them being more politically motivated than anything else, is equally disturbing and problematic. Both of these ways of governing lend themselves equally well to dictatorships, which I consider problematic, especially in modern democracies, which the US certainly claims to be (the Chinese government at least doesn't claim to be a democracy in the first place).