I think it depends on the individual and the circumstances of the upbringing.
You can get someone that was born elsewhere ,came here at a young age yet feels totally English/British.I have a friend who was born in the Ukraine, you couldn't meet a more cockney English bloke.I also have mates who are London born yet see themselves as 100% Irish.I get that . Though anything further down the line than that and it gets a bit silly IMHO.
I could (if I was good and young enough) play for ,as well as England, the Rep of Ireland and Northern Ireland.
England first and foremost with me(by a country mile) ,Northern Ireland,yes,but I would feel like a bloke invited to a party only because his mate was popular, but I would feel uncomfortable playing for the republic. No offence intended to anyone ,just wouldn't seem right.
Luckily for all involved I am 48 and play like football like I sing...