The reason why Facebook transferring data to the US is illegal in the EU is because its spy agencies and law enforcement can force them to turn over data.

It's not off topic at all.

Can EU governments force companies to turn over data? If not, then you are talking about what EU governments do secretly. That's a different topic.

And the United States can't? Facebook is part of PRISM, and they are incorporated in America. They are arguably in a more compromised state when operating domestically than abroad.

That's not the argument I would go with, but you could. I would argue that the EU has more oversight into its spy agencies and can reign them in if wrongdoing comes to light, whereas they have little to no control over those in the US.

It's not off topic. You said:

> unlike the US they largely enjoy that right thanks to laws which are enforced

This is categorically not true.