We can evaluate this by considering the results of DNS blocking ThePirateBay.
ref: https://kagi.com/search?q=How+effective+was+dns+blocking+the...
https://www.techradar.com/computing/cyber-security/facebooks...
This particular story seems moot to the worry porn viewers would have of Facebook ratting them out to law enforcement.
Government compliance depends on which government has jurisdiction, so it makes a lot of sense to avoid authoritarian jurisdictions.
e.g. NordVPN was originally Lithuanian, but is now based in Panama due to its privacy-friendly laws.
Results are references. Links pasted in HN can leave some doubt what's at the other end. Usually that's fine but by presenting those same links thru a search engine, you get some text to help indicate whether they have the info you want.
The results may also include links you would want - but maybe I wouldn't choose.
> Do you have a direct source for how many Americans accessed TPB after it was DNS blocked in all of the US?
This is a very narrow scenario you've presented. It doesn't seem to address the aspects of the thread in a helpful way.