Regional play is not actually by the government but by the media and by how you watch something.
I don't know the exact details but it's like this:
each region has a specific code in it's devices which can only play specific media. The media has a region specific code too. So if you have a USA computer and you try watching a British DVD on it, it won't let you, or it will make you choose a region, in which case your computer would no longer play DVDs from another region.
Youtube probably has the same sort of programming where users logging in from the USA can't access UK specific media.
Now, the reason for this isn't government. This is all FREE MARKET's doing. See, media companies dont want you accessing their material before they want to release it to you. That's why they will release TV shows or movies in the Europe but not release it in Australia or the USA until months later. If they sell the DVD before it's even in USA theaters, then Americans would be buying the DVD and having it shipped to them from the UK instead.
So no, it is not censorship.