TBH I disagree with your statement here. It's not just the USA that can do this. Europe and UK did this pretty successfully. Thanks to their legislation Facebook won't share data with WhatsApp.

But I agree what you say is true when it comes to emerging countries. But then again, maybe they do.

Take Brazil or India as examples. They have such massive population that if they wanted to, they could impose financial penalties to Facebook for doing that. The problem is figuring out if politicians in those countries have the incentive to do that though.