Kinda what Gary said.
It's a tricky one to be fair. I will add that there is a misconception that some lads jump ship because ROI are a better side and your prospects are better of going to a World Cup or whatever. That's shite. I, and any other Catholic I know from NI would play for the Republic. They're who I've supported my whole life, they're a closer resemblace to the Ireland I'm from, and they represent Ireland better to me.
If they were shite, I'd still have played for them. In fact, they are shite. They're just not as shite as NI if you know what I mean.
I will also add that NI football, it's administration, and it's fans have come on leaps and bounds in the last 15 years. A lot of it is down to good work from Jim Boyce and the IFA, getting rid of some shadier managers, etc etc. But I think most of the credit for the icreased bonhomie is down to the supporters and really the goodwill (or better will) on the stands is a refelction of Northern Irish society and a prefernce to move on rather than carrying the fucking fight on forever and a day. People, for the most part, were tired, and couldn't be fucked with it anymore.
It also coincided with better form for NI on the pitch. It was probably easier for the fans to concentrate on football than the other bullshit, cos they were beating England, Spain and the likes.
That said, there is still a way to go before Northern Irish born players will play for them as first choice. It's not wholly dissimilar to attitudes towards the country's police force, the PSNI. You can change, adapt, and become progressive, but it's hard to wipe away decades of history oernight and the IFA have to recognise that as far as they've come, they've still a long way to go. Which in fairness, they probably do recognise.