It's as offensive to us as colluding Koreans and Japanese would be to those countries.
Umm, no. In fact, absolutely not.
England = England.
Britain = England + Wales + Scotland.
U.K. = England + Wales + Scotland + N. Ireland.
Of all of these 'nations', the U.K. (United Kingdom of Great Britain and Northern Ireland) is the obnly one to enjoy full nation status, and the only one to be easily recognized by foreigners with little interest in the internal affairs of the U.K. (assuming the foreigner doesn't just call the whole collection 'England' and wash his hands of the details).
Japan, North Korea, and South Korea are all fully independent nations and not merely members of a larger political entity. As such, comparing them to Wales, England, or Scotland is inappropriate and out of context.
The not-so-simple system of unions employed by the U.K. (ie, why have two seperate systems: the U.K and Britain?) is far from common. Although, upon further thought America (with territories such as Puerto Rico, Guam, the Virgin Islands, etc) also has a similarly complex system. Maybe its related to imperialism? Maybe not.
The fact remains that Wales, England, Scotland, and N. Ireland are not fully independant countries. They are territories belonging to the greater whole of the United Kingdom. Similar (yet not identical to) provinces or states within any other kingdom. That, for me, is enough to view these four entities as 'regional players' who act under the umbrella of the United Kingdom, which acts as a global player.
Feel free to attack my logic in continuing to view England, Wales, etc as 'regional' distinctions, but at the very least you should concede that from the outsider's point of view, the political situation within the U.K. is not self-evident, and hardly the matter of global discourse. I'd expect the average foreigner to know the details of the U.K. political situation as much as I would expect the average Japanese (or American for that matter) citizen to know the 10 provinces and 3 territories of Canada off-hand.
Edit:
Thats actually a reasonable habit since the differences between 'England', 'Wales', 'Scotland', and 'North Ireland' don't trancend the regional.
Apparently I didn't express myself correctly. When i say the differences between these four entities don't transcend the regional, I mean the
knowledge of the differences (whether it be cultural/linguistic/traditional or simply political) between these entities does not transcend the regional. Public interest in the matter drops sharply once outside the region (The U.K. and possibly the EU).