If the last years have show us anything it is that the USA government (and others) can create the legality that they think more convenient.
For instance, you can invent a new category in order to avoid detaining people like criminals or war enemies if none of the laws applying to those are convenient.
True, and I wouldn't put it past them, but I know of no current legal mechanism for that. Emphasis on legal, of course.
It does make me wonder what they'd use for justification - prior to the current administration. The current administration would just use nationalism and protectionism, I'd think. I'm not sure how the previous administration would have framed it in order to make it politically feasible.
The federal government can forbid any of its employees from using the said service out of security concerns, a la Kaspersky. With network effect this can be an insurmountable challenge. Why should anyone try?
For the thought exercise, I suppose. With the already entrenched services, it seems unlikely to change to whole new services. At least not any time soon.
There were services that came before, but they lacked the inertia the current incumbents have. The userbase of Facebook, Google, etc. is huge in the Western world. Even if another company came along and built a great service, I doubt it would see mass adoption due to the massive numbers involved with the current providers.
They can still watch youtube videos about molecular biology all they want. The numbers don't really matter in that regard. And why would Google care if whatsapp is banned? Facebook didn't care that google search was banned.
Banning Facebook would actually give a boost to their productivity, not much to lose there.
For instance, you can invent a new category in order to avoid detaining people like criminals or war enemies if none of the laws applying to those are convenient.