I think every rational religious person would agree most people follow the religion of their parents. There are cases in the U. S. where a child rejects the god of his/her parents and latches on to another, but usually the child willl stay within Christianity. If parents had been Hindu, it would be the same. And we could name others.
But, the influence of demographics does not end with choosing a god. It also influences with brand of Christianity is followed. Protestant Christianity’s history has been one of denominations. These denominations split into further variations, but they remained denominations nevertheless.
Now, the very concept of denominations is under stress. Again, the reason is demographics.
In rural America, it was not that easy to change denominations. One was born into a location where there was limited choice in denominations and had a cultural linage that steered him/her toward the church of the parents.
As the march of rural to urban migration continued, those two forces became less and less important to each generation. There were churches in the neighborhood, but it was easy to chose one across town. Loyalty has decreased, jumping from church to church has increased.
On top of that there is the charity call in the urban area. If one finds a spiritual satisfaction in such charity work, it does not matter which denomination is chosen, the mission will be identical.
The demographics of urbanization have reduced the importance of denominations.