The UK itself is a country of the United Kingdom, and so of course the rest of the UK should aid effectively itself. If a US State fell into crisis, than the US Government should aid said State, just like the UK Government should aid Northern Ireland. Ireland, nor the USA or obliged to help, nor should they do so unless requested by the UK. Whether people like it or not, Northern Ireland is British. The British should help each other, the Americans and Irish, only if their aid is called for.
Yes, I think that if there is a crisis in the Northern Ireland that we need to jump in along with these other countries and try to go ahead and get it stopped quick, so that it does not spread on to a lot of other places that are close.
Most importantly, I think Ireland should try to intervene and settle things down. I do not think Northen Ireland wants the United States or the UK meddling in their affairs. Especially the UK. They are at odds with England especially, who would be spearheading the entire thing. Maybe the USA could help.
Yes, the UK and Ireland should definitely intervene when Northern Ireland experiences a crisis. The deadly violence that used to characterize part of the world could easily start breaking out again, which makes intervention a necessity. When it becomes clear that the UK and Ireland cannot provide adequate assistance to resolve the conflict, then the US should offer diplomatic assistance.
I think that any crisis that occurs in Northern Ireland should be handled by the governments of the UK and or Ireland. The USA should not get involved in such matters. Nor do they have any business in doing so. I think that the issues in the region is better left to those who govern it.
Personally I do not believe the United States has any reason to step in when there is a crisis in Northern Ireland. It might be in our best interest to send foreign aid or help out in a voluntary matter, but not at a political scale. If anyone was to step in it should be Ireland or the United Kingdom.