How did the split between muslims a long time ago affect today's generation of muslims

It affected them in a similar way as it affected the modern rome-catholic church and the orthodox faith for example. While you have religions from the same culture and same religion, it's not completely the same. On the other hand you can say the same thing and find the same thing in the muslim religion where people are either Sunni or Shia and they are not bothered by it.