IMHO you're kinda right. There's a trade war going on between the US and China, and data is damn valuable so it's just logical to prevent the enemy access to your own citizens' data, specially since we know how it's used to manipulate elections (Russia's been proven guilty of it for the 2016 US elections), but also Facebook was at least paid to do so.
Now I do agree with you in that the ban is probably due to the wrong reasons though. But it kinda doesn't matter to me.

Yet I am not US citizen either, I'm an EU citizen, so my opinion on US politics ain't quite relevant. I just wished we would do the same here in Europe and more consequently. Both the US and China do have laws that require companies to hand over there user data to their respective country's agencies, which is technically illegal under GDPR for EU citizens' data (they shouldn't be able to leave the EU). So we should ban all social media that stores data on servers belonging to US or Chinese companies (leaving basically only fediverse instances on european servers).