Virtually all nationalities are allowed to enter the green card lottery. UK citizens are one of the few that can't. What is this 'special relationship' they speak of. As far as the US is concerned we appear to be lepers.
If you actually understood the conditions of the Green Card Lottery, you would realize that the UK's ineligibility is precisely because so many UK citizens immigrate to the United States under normal channels. Did you know that the real name of the lottery is the Diversity Visa lottery? It's really a bit of a stretch to argue that adding more Brits contributes in a meaningful way to US diversity.
If you look at the
instructions, you'll see that the UK's ineligibility has nothing to do with being "lepers" or some other similar stupid complaint. The UK, like a bunch of other countries, has sent more than 50,000 immigrants to the United States over the past 5 years, which makes it ineligible for the lottery. In fact, a key reason for the UK's status is precisely that lots of UK folk move to the US on family or employment-related visas. If you want to whine about your Green Card Lottery exclusion, blame all the Brits with US relatives who sponsor them, and all the companies who sponsor UK citizens to work in America.
The other countries currently ineligible include Brazil, Canada, China (mainland-born), Colombia, Dominican Republic, Ecuador, El Salvador, Guatemala, Haiti, India, Jamaica, Mexico, Pakistan, Peru, Philippines, Poland, South Korea.
I can't explain the Northern Ireland exemption; i assume it's probably due to some lobbying from the large Irish contingent in the US. America certainly doesn't need more Irish for its diversity, either.