U2 is my new favorite band, but I don't know alot about them.
Well they are a Irish rock band that started in Dublin in 1976.
Did their Irish culture shape their music? 
Well their music has often been said to often embellished with spiritual imagery. They focus on personal and sociopolitical themes. 
Are they a Christian rock music band. 
No though initially they had been rooted in post-punk. They have evolved a lot over the years.