Yes I've lived in Liverpool so I know what you mean, the religious divide is pretty much ancient history on Merseyside. Then again Liverpool is a city with a considerable percentage of the population (30% ?) from Irish descent and as a result (I think I'm right in saying) has the highest Catholic population of any city in England, so it's not surprising that there used to be division.
Unfortunately NI is not the same, as for most people their religion still determines their nationality. Whereas in Liverpool everyone accepts that they are English, most people from one religious persuasion in NI won't accept that they are Irish despite the fact that they live here. So it's really about nationality rather than religion, which as you say is no longer an issue in Liverpool. Until the nationality issue is resolved the division is set to continue.
not sure of the current figures but around 2000 there were a few articles saying that it was 43% catholic which was the highest in the UK , last year was the first year for catholics overtaking the church of England as the the highest number of people in the UK that actually went to church, boris johnson had a bus saying it was because of poles taking are pews

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yep lots of Irish descent here and a very large welsh one that mainly gets overlooked .
although the area going back centuries has even before immigration a long history of catholic worship, likes of little crosby even during the reformation staying firmly within the church.
not remotely into it myself , although i do pop into church now and again as it brings back memories of people that used to go with me as a kid. i like the surroundings weirdly for some reason, must be nice to have faith looks comforting to those that have.