Visiting the Heineken website in the U.S. requires that you assert you are over the age of 21. Texas has instituted I.D. verification for pornography.
Regardless of how you feel about this law, it is not accurate to say the U.K. is unique in implementing it.
Just, no.
5-eyes is the most heinous human-rights-destroying apparatus under the sun, and it wouldn't be happening if it weren't for the British desire to undermine cultures they have deemed inferior.