They should simply give Ireland back to the Irish, and Scotland back to the Scots.
Actually, they should take back the African colonies. The Africans haven't demonstrated the ability to run their continent or a country. The world is much better with Americans in charge of America instead of the Indians. Africa would be much better if it were run by the British.
There is no inherent advantage of the British running Ireland.
"The Brits gave India back to the Indians."
Great example that bears some thought. You had a mass of ethnic groups which the British Raj had held together (through means fair and foul). When we went the first thing the population did was split off Goa which wanted to remain Chritian, and then there was one of the largest population moves in history when a massive chunk of the Muslim population decided to had to a Northern enclave and start a country called Pakistan. Non mulsims in what is now Pakistan made the journey south the other way to live in the new smaller India. Most folk seem to think the Status Quo reasonable (even if their are no fans of Pakistan here!)
How is that different to when Ireland was made independent but Ulster did not want to belong to the republic. Lots of Prod's moved North, lots of Catholics mooved south. Ulster did not want independence like say, Pakistan, it WANTED to remain part of the UK. The division frankly prevented ethnic cleansing of the whole island.
The problem I find with these discussion is thaat some "Irish-Americans" read propoganda from Sien Fein and feel that because their great-great-great grandparents left the mess for America they should toe the Sien Fein nonsense to somehow affirm their roots. The warm glow they get when they stick their dollar bills in the Noraid jar while supping imported guiness and listening to an irish piper in a pseudo irish bar seems to help cement some identity. You see lots of this in places like Boston and New York. The problem is, for too long, that dollar in the Noraid jar paid for bullets into folks kneecaps or worse. The lack of knowledge is depressing. You can't get past the potatoe famine in the discussion as if this somehow legitimises late 20th centry bombs in shopping malls and random murders.
All four of my grandparents were Irish, which probably makes me more Irish then most 'Irish Americans'. Fortunatley, I was able to actually meet and talk to this part of my ancestory and gain a fair perspective (my mothers side catholic, my fathers side protestant). Both sets had horrific experiences in the 1920s which forced them to the mainland (it's fair to say they didn't like each other and didn't approve of the wedding!). Northern Ireland is a free country. When the catholic population finally overtakes the protestant population, which due to protestants having far few children will almost certainly happen in our lifetime, perhaps then they will unite. But they can do so democratically - no bombs needed.